1. Feng, J., Bhargava, H.K., Pennock, D.: Comparison of allocation rules for paid placement advertising in search engines. In: Proceedings of the fifth International Conference on Electronic Commerce, Pittsburgh, PA, USA (2003)
2. Goodman, J.: Pay-per-percentage of impressions: an advertising method that is highly robust to fraud. In: Workshop on Sponsored Search Auctions (2005)
3. http://adwords.google.com
4. Bhargava, H., Feng, J., Pennock, D.: Implementing paid placement in web search engines: Computational evaluation of alternative mechanisms, accepted by informs journal of computing. To appear in the Informs Journal of Computing
5. Mitchell, D.: Click fraud and halli-bloggers. New York Times (July 16, 2005)