2. 1 Informatie gratis vinden via Internet Finding information through Internet free of charge Paul.Nieuwenhuysen@vub.ac.be Vrije Universiteit Brussel Presented at VUB Campus Etterbeek, October 26, 2000 Campus Jette, November 18, 2000 http://www.vub.ac.be/BIBLIO/nieuwenhuysen/presentations/

3. 2 Online access information sources and services Introduction

4. 3 Internet based information sources: problems too much of it / redundancy too few of some no order / no quality checks / no requirement to register new information offered constantly changing / increasing / growing authenticity?

5. 4 Internet based information sources: how many? how much? In 2000: about 1 000 million unique URLs in the total Internet about 10 terabyte (= 10 000 gigabyte) of text data

6. 5 Types of online access information systems: “free” versus “fee” Public access information sources free of charge Fee-based online information services (NOT free of charge)

7. 6 Types of online access information systems: “free” for members only Public access information sources free of charge Fee-based online information services (NOT free of charge) Fee-based online information services, made accessible “free of charge” by an institute to its members

8. 7 Online access information sources and services Internet-based encyclopedias

9. 8 Encyclopedias accessible through Internet and WWW Some encyclopedias and dictionaries are available through the WWW free of charge.

10. 9 Encyclopedias accessible through Internet and WWW: examples Encyclopædia Britannica including Merrian Webster dictionary + links to selected WWW sites http://www.britannica.com/ http://www.britannica.com/ Encarta Concise Free Encyclopedia http://encarta.msn.com/ http://encarta.msn.com/ A list of encyclopedia on the Internet: http://www.internetoracle.com/encyclop.htm http://www.internetoracle.com/encyclop.htm Other lists of encyclopedia on Internet can be found as a part of browsable Internet directories.

11. 10 Online access information sources and services Internet directories and indexes

12. 11 Internet: subject-oriented meta- information offered via WWW Information about information sources: in the form of »subject guides = texts with references »subject hypertext directories = subject guides »key word indexes, generated automatically, for searching »collections of links or forms to the above »(multi-threaded search systems)

13. 12 Internet global subject directories: introduction They are virtual libraries with open shelves, manually generated, man-made, for browsing. They cover only a small number of selected WWW sites. They are suitable mainly for broad, not very specific searches that are difficult to formulate in words. They can include an index on the contents of the directory (which may be confusing, as they are not real Internet indexes)

14. 13 Internet global subject directories: Yahoo! A hypertext global subject directory can be found at http://www.yahoo.com/http://www.yahoo.com/ and at many other sites, including http://www.yahoo.co.uk/ http://www.yahoo.co.uk/ Entries are not rated. Accessible free of charge. When the directory of Yahoo! does not provide results, Yahoo! uses a much larger external Internet index to execute a query based on textual search statements. The chosen Internet indexes have varied over time.

15. 14 Internet global subject directories: Britannica A hypertext global subject directory can be found at http://britannica.com/ http://britannica.com/ Entries are rated. Accessible free of charge.

16. 15 Internet global subject directories: BUBL A hypertext global subject directory can be found at http://bubl.ac.uk/ http://bubl.ac.uk/ Accessible free of charge.

17. 16 Internet global subject guides: The Argus Clearinghouse A collection of subject guides is made available at http://www.clearinghouse.net/ http://www.clearinghouse.net/ Accessible free of charge.

18. 17 Internet global subject directories: Google A hypertext global subject directory can be found at http://directory.google.com/ http://directory.google.com/ Accessible free of charge.

19. 18 Internet global subject directories: LookSmart A hypertext global subject directory can be found at http://www.looksmart.com/ http://www.looksmart.com/ Links are offered to LookSmart by the Internet index AltaVista. A search in the LookSmart index is also executed with the Internet index AltaVista. Accessible free of charge.

20. 19 Internet global subject directories: Resource Discovery Network A collection of hypertext subject directories that focus on academic information sources can be found at http://www.rdn.ac.uk http://www.rdn.ac.uk Accessible free of charge.

21. 20 Internet subject directories: non-global, more specific systems a directory restricted to a specific subject domain a directory limited to sources in/of a country or region a global subject directory the complete WWW

22. 21 Internet subject directories focusing on a specific subject domain Social sciences: http://www.sosig.ac.uk/http://www.sosig.ac.uk/ Medicine and healthcare: http://www.omni.ac.uk/http://www.omni.ac.uk/ Engineering: http://www.eevl.ac.uk/http://www.eevl.ac.uk/ Computer science & engineering: http://www.ub.lu.se/eel/http://www.ub.lu.se/eel/ Art, architecture and the media: http://www.adam.ac.uk/http://www.adam.ac.uk/

23. 22 Internet local subject directories: examples in Belgium http://yellow.advalvas.be/weblist.html http://search.msn.be/exploring/exploring.asp The guide developed by the public libraries in Flanders: http://www.bib.vlaanderen.be/webwijzer http://www.bib.vlaanderen.be/webwijzer

24. 23 Internet indexes: automated search tools Several systems allow to search for and to locate many items (addressable resources) in the Internet in a more systematic way than by only browsing/navigating. Each of these search systems is based on: »a database of links to URLs, continuously collected from the Internet by a “robot” and incorporated in their big index, that is “machine-made” »a search system with a user interface in a WWW form, to allow the user to search through that database

25. 24 Internet indexes: scheme User searching for Internet based information Internet client hardware and software user interface to a search engine Internet information source Internet index search engine Internet crawler and indexing system database of Internet files, including an index

26. 25 Internet indexes: AltaVista The primary search interface can be found in the US: http://www.altavista.digital.com/ http://www.altavista.com/ http://www.av.com/ (These addresses all lead to the same information.) Mirror site in UK: http://www.altavista.co.uk/

27. 26 Internet indexes: AltaVista: features Allows full text searching »of WWW, with a good coverage »(of Usenet newsgroups archives) Allows advanced Boolean searching (in “Advanced” mode) Offers relevance ranking of search results Offers a link to an Internet subject directory (Looksmart) Offers links to systems to find images, sounds,… (multimedia) in the Internet

28. 27 Internet indexes: AltaVista simple versus advanced “Simple” is suited for instance for searches »with only 1 concept expressed as a series of synonyms, narrower terms,... such as a search for a person, a company, an institute,... »when ranking is important “Advanced” is suited for instance for searches »with more than 1 concept so that an AND combination is useful, besides an OR combination »when ranking is not important

29. 28 Internet indexes: AltaVista for citation searching AltaVista allows you to search for documents / pages / URLs that link to a particular page, to some URL that you already know (such as one of the web pages that you have developed or that you have made available yourself). Linking to a URL is similar to citing an information source. So AltaVista can be used to analyse web citations. See the online manual for the query syntax.

30. 29 Internet indexes: citation searching on the WWW Citation searching on the WWW or on an intranet can be used »to get an idea of the importance, the fame, the impact of a particular web page, as measured by the number of links/citations to that page »to find out who has considered a particular page as interesting enough to make a link to »to find comments/criticisms on a particular web page

31. 30 Internet indexes: Fast = All the Web The search interface can be found at: http://www.alltheweb.com/ http://www.alltheweb.com/ You can search the Web and ftp servers. The database is one of the biggest.

32. 31 Internet indexes: Google The search interface can be found at http://www.google.com/ http://www.google.com/ You can search for Web content. Does NOT offer/allow full Boolean searches. Does NOT offer/allow stemming/truncation! Uses an algorithm based on the links between pages. A retrieved page is ranked higher when »“important” sites point to it »many sites point to it

33. 32 Internet indexes: Northern Light The search interface can be found at http://www.northernlight.com/ http://www.northernlight.com/ You can search »free Web content and »some other publications (full text articles) (but obtaining the text is not free of charge) Warning: searching with synonyms or related words together in the same simple query can result in a smaller and not in a larger set of results!?

34. 33 Internet indexes: Northern Light categories Each source is categorized/classified automatically off-line in several categories/classes »using a statistical analysis of its contents, and »using a hierarchical classification system with thousands of categories/classes. With each result of a search, the categories/classes in which it is classified are displayed. In this way Northern Light is a machine made Internet index similar to a man-made Internet directory.

35. 34 Internet indexes: Northern Light categories illustrated Searching for pascal yields the following categories: Your search returned 724,059 items which we have organized into the following Custom Search Folders: Search Current News Special Collection documents Pascal Delphi (programming language) Gambling vein.hu Oberon Cryptography Geometry Internet Silicon Graphics workstations Philosophy Computer software industry all others... Pascal can indeed be a computer language, a philosopher,…

36. 35 Internet indexes: Northern Light alerts For current awareness and news, you can set up private, personal search alerts in Northern Light. New search results are brought to your attention through an email message that offers a link for each “alert” to WWW.

37. 36 Internet indexes: coverage / size of each index The indexes grow and their “size ranking” is variable. In 2000: 1. AltaVista; Fast = All the Web; Google; Northern Light;… 2. Infoseek; Hotbot; MSN Web Search; Snap!; Excite; Euroseek;... 3 Webcrawler;...

38. 37 Internet indexes: delay in indexing new pages The great, well known, international Internet indexes have a delay of more than 1 month in indexing new pages. (according to Lawrence and Lee Giles, Nature, 1999, Vol. 400, pp. 107-109.) So they are not suitable to search for rapidly changing recent information (such as “news”) (unless they index a small selection of important news sites more frequently.)

39. 38 the complete WWW a global Internet index an index limited to sources in/of a country or region Internet indexes: non-global, regional systems

40. 39 Internet indexes: evaluation criteria (Part 1) Is usage free of charge? Wide coverage? Specialized coverage? (more news, only one country,…?) Up to date? Frequent updates? Only few dead / broken links?

41. 40 Internet indexes: evaluation criteria (Part 2) Is spamming filtered out? Full text indexing of each ASCII and HTML document in the database, so that full text searching is possible? Indexing of the contents of meta-fields? Also indexing of text in non-ASCII files? for instance files in the format of »Microsoft Word »Microsoft PowerPoint »Adobe Acrobat (Portable Document Format)

42. 41 Internet indexes: evaluation criteria (Part 3) Field indexing, so that searching for the contents of a particular field is possible? for instance: the HTML title,HTML keywords, URL, date, link,Java applet, text, image file, sound file,video file,...

43. 42 Internet indexes: evaluation criteria (Part 4) Powerful search options: »truncation? »word stemming? »Boolean search combinations? »proximity searching? »translation of your search terms in several other languages? »spelling check of your search terms?

44. 43 Internet indexes: evaluation criteria (Part 5) Can the results be limited to a certain time period? For instance based on the date »of the file as noted by the server computer, or »of the most recent indexing of the file Easy user interface? Is a user interface offered in your own language? Relevance ranking of results?

45. 44 Internet indexes: evaluation criteria (Part 6) Possibility to combine Boolean retrieval with relevance ranking of results? Can the results be ordered according to date »of the file as noted by the server computer, or »of the most recent indexing of the file Can the results be ordered according to size? Can all the results (documents) from the same site be grouped together?

46. 45 Internet indexes: evaluation criteria (Part 7) Can the system cluster or eliminate presumed duplicate documents in the results? Can the system rank the results (documents) on the basis of the number of WWW hyperlinks to that document? The system does not place/rank some results (documents) higher in the results list, on the basis of payments by the producer of those documents to the search system company.

47. 46 Internet indexes: evaluation criteria (Part 8) Short response times? Are mirror sites available closer to you for faster response? Good presentation format of each result (document)? Are search terms indicated / highlighted in the results? Good and detailed summary of each result available? Offers an analysis of words occurring in the results, which can help you to refine a search?

48. 47 Internet indexes: evaluation criteria (Part 9) Is translation of documents offered free of charge? High stability and reliability? No large variations/fluctuations in the results from identical searches at different times. Good documentation and online help? Good help desk available? Can the search system provide updated results through electronic mail, as a current awareness tool?

49. 48 Internet indexes: evaluation criteria (Part 10) Other services available besides the normal WWW index: »index to news resources, that is more frequently updated? »anonymous ftp file index? »Gopher index? »searchable Usenet newsgroups archive? »Internet subject directory? »White pages = people finder = addresses =... »WWW-based e-mail and e-mail address directories »auctions through WWW

50. 49 Internet indexes: evaluation criteria (Part 11) Is the search/query also submitted to another database to obtain more results? for instance: to a book database to obtain book descriptions besides WWW documents

51. 50 Internet indexes cover only a part of the Internet: introduction The “visible” part of Internet The “hidden, invisible” part of Internet, (not searchable using a global index like AltaVista, Northern Light,...)

52. 51 Internet Internet indexes cover only a part of the Internet: scheme WWW Databases and file archives accessible through the Internet telnet ftp... telnet ftp... CGI,... Rapidly changing information, such as news Information accessible only when passwords are used Static indexable texts in the WWW ( = on HTTP server computers) covered partly by Internet indexes

53. 52 Internet indexes cover only a part of the Internet: conclusion for users When you want to retrieve information about a particular subject from the Internet, use not only WWW indexes, but use also other sources accessible through the Internet »databases (book and journal bibliographies, library catalogues, archives of group messages, directories, atlases,…) »rapidly changing information, such as news »anonymous ftp file archives, »e-mail based interest groups; Usenet newsgroups, »information accessible only when passwords are used

54. 53 Multi-threaded Internet search systems: scheme User Client computer + WWW client program WWW server computer Internet WWW WWW server computers with Internet search systems In Out

55. 54 Multi-threaded Internet search systems: vocabulary “multi-threaded Internet search systems” “multiple search systems” “multisearch systems” “metasearch systems” “intelligent Internet search agents” “Internet metasearch tools”...

56. 55 Multi-threaded Internet search systems: relations User an Internet meta search system Internet search system 1 Internet search system database 1 WWW pages Internet search system 2 Internet search system database 2

57. 56 Internet information sources Coverage of Internet directories and Internet indexes A global Internet index A global Internet directory

58. 57 Hybrid systems to find information on the Internet Some systems require a search in words from the searcher, but they do not rely on classical Internet indexes. Example: Ask Jeeves

59. 58 Hybrid systems to find information on the Internet: Ask Jeeves Ask Jeeves “answers questions” of searchers, by analysing the natural languages queries and by referring to selected sources on the Internet. http://www.askjeeves.com/ http://www.ask.com/ http://www.aj.com/

60. 59 Global Internet search tools: a comparison Global Internet directories Only a limited selection of Internet sources Browsing information sources is easy Good for broad searches Global Internet indexes About 1/3 of the Internet is covered by an index Searching requires some skills and knowledge Good for specific, narrow searches Multi-threaded search engines Gets information from directories and indexes Searching requires some skills and knowledge Good when even 1 index does not yield information

61. 60 Finding multimedia files on the Internet: introduction Several public access search systems are available free of charge to search the Internet for multimedia files: »sound / audio files (music, speeches,...) »images / pictures (either artwork, either photos, or both) »video

62. 61 Finding images on the Internet: introduction Several public access search systems are available free of charge to search for images / pictures (either artwork, either photos, or both) on the Internet. The search results offer not only links, but also directly small versions of the images (= “thumbnails”)

63. 62 Finding images on the Internet: examples of image search engines http://www.altavista.com/ also audio and video choose not the normal text search, but IMAGES in the user interfacehttp://www.altavista.com/ (http://ipix.yahoo.com/)http://ipix.yahoo.com/ http://scour.net/(also audio and video)http://scour.net/ http://www.ditto.com/...

64. 63 Guide to searching the Internet available through WWW Searching the Internet: recommended sites and search techniques. [Online] Available from: http://www.albany.edu/library/internet/search.html http://www.albany.edu/library/internet/search.html The RDN virtual training suite. [Online] Available from: http://www.vts.rdn.ac.uk/ offers training for users with a specific academic or professional interest. http://www.vts.rdn.ac.uk/

65. 64 Tracking changes in WWW pages Tracking changes in one or more public access pages on the WWW is possible through specialised services. Such services can be accessed through the WWW. Several of these services are free of charge. Example: http://mindit.netmind.com/http://mindit.netmind.com/

66. 65 Online access information sources and services Public access book databases

67. 66 Public access book databases: an overview (Databases by publishers.) Databases by book distributors / bookshops! Online public access library catalogues (Databases of computer-based versions of books.)

68. 67 WWW Examples of free public access bibliographic book databases (Part 1) Amazon.com (US): http://www.amazon.com/ http://www.amazon.co.uk/ note: amazon, NOT amazone http://www.amazon.com/http://www.amazon.co.uk/ Barnes and Noble (US): http://www.bn.com/ http://www.bn.com/ Blackwell’s on the Internet (International, academic books): http://www.blackwell.co.uk/ http://www.blackwell.co.uk/

69. 68 WWW Examples of free public access bibliographic book databases (Part 2) VLB (for books in German) http://www.buchhandel.de/ http://www.buchhandel.de/ Boeknet - De Nederlandse Internet Boekhandel (Dutch) http://www.boeknet.nl/ http://www.boeknet.nl/ Proxis (Belgium) http://www.proxis.be/ http://www.proxis.be/ Virtual Book Shop (good for old books) http://www.bookshop.com/ http://www.bookshop.com/

70. 69 WWW Free public access bibliographic book database + price comparisons For books, music, movies and many other goods: www.dealtime.com www.dealtime.com

71. 70 WWW Example of an international public access dissertation database The dissertation database of UMI is available from: http://wwwlib.umi.com/dissertations/ A part is available free of charge. http://wwwlib.umi.com/dissertations/

72. 71 WWW Database of links to the full text of many books A database (accessible free of charge ) of links to the full text of many books: http://digital.library.upenn.edu/books/ http://digital.library.upenn.edu/books/

73. 72 Online access information sources and services Online Public Access Catalogues = OPACs

74. 73 Online Public Access Catalogues = OPACs: definition Online Public Access Catalogue: a term used to describe any type of computerized library catalog offered to the public by online login

75. 74 Online access library catalogues: The British Library In 1997: http://opac97.bl.uk/ http://opac97.bl.uk/ Accessible online via WWW Access free of charge

76. 75 Online access library catalogues: The Library of Congress, U.S.A. >15 million books + >10 million other documents In Washington DC, U.S.A. Accessible online via WWW Access free of charge

77. 76 Online access information sources and services Online access databases about journal articles

78. 77 Online access databases about journal articles: overview Thousands of fee-based online access databases offer bibliographies or full-texts of journal articles in particular subject domains. Only few large databases offer access to bibliographies of articles published in journals, free of charge.

79. 78 Online access databases about journal articles: Northern Light Northern Light allows searching for »WWW documents »the full text of articles from many journals/magazines Searching is free of charge. Available from »http://www.northernlight.com/http://www.northernlight.com/ »http://www.nlsearch.com/http://www.nlsearch.com/ Payment is required to receive the full text of an article.

80. 79 Online access databases about journal articles: Ingenta (1) Ingenta Journals allows you to search a bibliographic database of millions of journal articles, including titles, authors, in many cases abstracts. Searching is free of charge.

81. 80 Online access databases about journal articles: Ingenta (2) Payment is required to receive the full text of an article. Ingenta has acquired Uncover in 2000. Available from »http://www.ingenta.co.uk/http://www.ingenta.co.uk/ »http://www.ingenta.com/http://www.ingenta.com

82. 81 Online access databases about journal articles: Article@INIST Article@INIST allows you to search in a bibliographic database, NOT full-text (Journal articles, Journal issues, Books, Reports or Conferences, doctoral dissertations) at the Institut de l'Information Scientifique et Technique, France. Searching is free of charge. Available from http://form.inist.fr/public/eng/conslt.htm http://form.inist.fr/public/eng/conslt.htm Payment is required to receive the full text of an article.

83. 82 Online access databases about journal articles: Eric Eric allows searching a bibliographic database of articles and other documents in the fields of information science and education Searching is free of charge Available from http://ericir.syr.edu/Eric/ http://ericir.syr.edu/Eric/ Payment is required to receive the full text of a document.

84. 83 Online access databases about journal articles: Medline Medline allows searching a bibliographic database of articles in the field of medicine. free of charge available from many sites, including Ingenta

85. 84 Online access information sources and services Electronic newsletters and journals

86. 85 Electronic newsletters and journals: various types and the price of access Various types: »equivalents of a version printed on paper »purely electronic publications Access: from free of charge to very expensive Author / Sender Editor Reader / Receiver

87. 86 Electronic newsletters and journals: access and distribution methods Many different methods are used: »anonymous ftp »gopher »WAIS »http, WWW ! »electronic mail »Usenet News »loaded on local systems in universities or institutes »...

88. 87 Electronic newsletters and journals: problems There is no central database with all article titles, summaries, and full contents. There is not even a central, complete and up to date directory of journal titles. Not all electronic journals are accessible through 1 user interface. Many passwords must be used. There is no standard licencing.

89. 88 Online access information sources and services Computer-based information sources: criteria to evaluate their quality

90. 89 Computer-based information sources: The Internet Detective A tutorial in English about how to assess the quality of WWW-based information resources can be accessed online free of charge through the WWW: http://sosig.esrc.bris.ac.uk/desire/internet-detective.html http://sosig.esrc.bris.ac.uk/desire/internet-detective.html A version for offline use is also available.

91. 90 Computer-network interest groups Introduction

92. 91 Computer network interest group system Computer-network interest groups: the basic scheme ? Question ? ! Answer ! E-mail

93. 92 Computer-network interest groups: various existing systems “Conferences” on computer-services like »AOL »CompuServe »Dialog »Data-Star »many Bulletin Board Systems »... E-mail lists ! Usenet News !

94. 93 Computer-network interest groups: aims and applications Searching and finding (up to date) information ! Developing your network of professional contacts Developing your network of personal contacts Telling others about your experience Expanding your customer base Bargain hunting Finding a job Voicing your opinion...

95. 94 Computer-network interest groups: searchable archives Past messages to many interest groups are kept in online archives. These may be browsed and searched. They provide a useful source of up-to-date information in various subject areas.

96. 95 Computer-network interest groups E-mail - based interest groups

97. 96 E-mail - based interest groups: synonyms E-mail (based) conferences Computer (based)(discussion) lists Network (based)discussion groups forums interest groups Listservs Reflectors Aliases

98. 97 E-mail - based interest groups: How to find relevant groups? You can (use printed directories of interest groups) use subject-oriented indexes and directories to search for Internet-based sources in general search directory files concerning interest groups online! Examples: »http://www.egroups.com/http://www.egroups.com/ »http://www.liszt.com/http://www.liszt.com/

99. 98 Archive of e-mail - based groups searchable online A partial archive of many e-mail - based groups is available. Usage is free of charge. Available from: http://www.egroups.com/ http://www.egroups.com/

100. 99 Computer-network interest groups Usenet News

101. 100 Usenet News: what it is Usenet is a worldwide computer-network conferencing system. Usenet is the set of people who exchange articles tagged with one or more universally recognized labels, called “newsgroups” (or “groups” for short). Usenet  Usenet server computers  Usenet clients

102. 101 Usenet newsgroups form a hierarchical structure Newsgroups are organized by subject area into a multi-layered hierarchy ( = tree-structure). This helps the users to find the “right” newsgroups.

103. 102 Usenet newsgroups form a hierarchical structure: an example... alt comp recscisoctalk...... binaries infosystems lang os...... gopher kiosks wais www...... misc providers users...

104. 103 Archives of Usenet newsgroups searchable online Several partial archives of Usenet News are available through WWW. They are searchable online. Usage is free of charge.

105. 104 Archives of Usenet newsgroups searchable online: examples Offering a good searchable Usenet archive: http://www.deja.com/ Offering a searchable WWW index + Usenet archive: http://www.altavista.comhttp://www.altavista.com/

106. 105 A current awareness service that covers Usenet newsgroups A current awareness service covering Usenet newsgroups sends you an e-mail message with information about each Usenet newsgroup message that matches an interest profile which you have submitted to the system. You can access the system through http://www.deja.com/ http://www.deja.com/

107. 106 Computer-network interest groups E-mail groups and Usenet News considered together

108. 107 Computer-network interest groups: How to find relevant groups? You can (use printed directories of interest groups) use subject-oriented indexes and directories to search for Internet-based sources in general search directory files concerning interest groups online search Usenet archives and identify those newsgroups from which relevant messages are retrieved ! (subscribe to a Usenet current awareness service, and identify those newsgroups which yield relevant messages)

109. 108 Computer-network interest groups: online searchable directories About e-mail groups »http://www.egroups.com/http://www.egroups.com/ About both e-mail groups and Usenet newsgroups »http://n2h2.com/KOVACS/http://n2h2.com/KOVACS/ »http://paml.alastra.com/http://paml.alastra.com/ »http://tile.net/http://tile.net/ »http://www.liszt.com/http://www.liszt.com/

110. 109 Online access information sources and services Future trends

111. 110 Online access information: future trends Increasing amount of information available online. Increasing amount of information available online and free of charge. Increasing quality of server and client software. Increasing number of end-users searching for information online.

112. 111 Informatie gratis vinden via Internet Finding information through Internet free of charge Paul Nieuwenhuysen pnieuwen@vub.ac.be Vrije Universiteit Brussel Presented at VUB, Brussels, October 26, 2000 http://www.vub.ac.be/BIBLIO/nieuwenhuysen/presentations/