Takayuki Yumoto   Katsumi Tanaka   
DIGITAL LIBRARIES: ACHIEVEMENTS, CHALLENGES AND OPPORTUNITIES, PROCEEDINGS 4312 244-+ 2006年 [査読有り]
Conventional Web search engines rank their searched results page by page. That is, conventionally, the information unit for both searching and ranking is a single Web page. There are, however, cases where a set of searched pages shows a better sim...