In addition there's long standing research in the field of Library Science about the importance of citations. It seems like a natural progression from judging t

In addition there's long standing research in the field of Library Science about the importance of citations. It seems like a natural progression from judging the quality of a paper by the number and quality of papers citing it, to PageRank. This book basically described something very similar to PageRank in 1993 (5 years before Google): http://www.amazon.com/Library-Research-Models-Classification-Cataloging/dp/019509395X http://www.amazon.com/Library-Research-Models-Classification...