I'd like to point out that the following websites contain a wealth of
material in the form of published and unpublished papers on various subjects
ranging all the way from physical to cognitive sciences.
PubMed Central is a digital archive of life sciences journal literature
managed by the National Center for Biotechnology Information (NCBI) at the
U.S. National Library of Medicine (NLM). It is not a journal publisher.
Access to PubMed Central (PMC) is free and unrestricted
My apologies to those who're already familiar with these.
Muhammad Ajmal Khan
National University of Computer and Emerging Sciences,
852-B Faisal Town, Lahore-54700, Pakistan