Project Euclid (Popularity: )
http://projecteuclid.org/ Full text access to the journal Annals of Mathematics; a limited number of other journals available through paid subscriptions to ...
My OAI (Popularity: )
http://www.myoai.com/ A full-featured search engine for most of the major E-print/preprint servers. Easy to use advanced search features. Use it as ...
CiteSeer.ist (Popularity: )
http://citeseer.ist.psu.edu/ E-print database of mathematics and science papers with citation information. Papers may be added by specifying the URL where their ...