http://citeseer.ist.psu.edu/ CiteSeer is a scientific literature digital library and search engine that focuses primarily on the literature in computer and information science. Developed in 1997 at the NEC Research Institute, Princeton, New Jersey, by Steve Lawrence, Lee Giles and Kurt Bollacker, it is now hosted at the Pennsylvania State University's College of Information Sciences and Technology under the direction of Professor Lee Giles.
Rather than creating just another digital library, CiteSeer attempts to provide resources such as algorithms, data, metadata, services, techniques, and software that can be used to promote other digital libraries. CiteSeer indexes PostScript and PDF research articles on the Web, and was the first digital library and search engine to provide automated citation indexing and citation linking using the method of autonomous citation indexing.