introduction to information retrieval christopher d . manning , prabhakar raghavan , and hinrich schtze ( stanford university , yahoo ! research , and university of stuttgart ) cambridge : cambridge university press , 2008 , xxi + 482 pp ; hardbound , isbn 978 - 0 - 521 - 86571 - 5 , $ 60 . 00 .
Optimizing search engines using clickthrough data