Footnotes

...Pinkas
Research partly supported by an Eshkol fellowship from the Israeli Ministry of Science
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...behalf.
Examples of such third-party services include ClickTrade ( http://clicktrade.linkexchange.com/), eAds ( http://www.eads.com/), and ValueClick ( http://www.valueclick.com/).
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...page.
See BannerNetwork ( http://adnetwork.linkexchange.com) and BannerSwap ( http://www.bannerswap.com/).
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...privacy.
Example privacy-enhancing proxies include the Anonymizer ( http://www.anonymizer.com) and the Lucent Personalized Web Assistant (http://lpwa.com).
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...pageR.html.
For example, InfoSeek (http://www.infoseek.com) explicitly offers the ability to query for such information, via a "field search" using the syntax link:pageR.
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...engines.
Search engine spider queries can be easily identified as such. For example, see http://searchenginewatch.com/webmasters/spiders.html.
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...site.
An example is the Associates program run by Amazon (http://www.amazon.com).
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Mike Reiter BL01123
3/9/1999