For articles that are published in closed access journals, some authors will deposit a postprint copy in an open access repository, where it can be accessed for free. Most subscription journals place restrictions on which version of the work may be shared and/or require an embargo period following the original date of publication. What is deposited can therefore vary, either a preprint or the peer-reviewed postprint, either the author's refereed and revised final draft or the publisher's version of record, either immediately deposited or after several years. Repositories may be specific to an institution, a discipline (e.g.arXiv), a scholarly society (e.g. MLA's CORE Repository), or a funder (e.g. PMC). Although the practice was first formally proposed in 1994, self-archiving was already being practiced by some computer scientists in local FTP archives in the 1980s (later harvested by CiteSeer). The SHERPA/RoMEO site maintains a list of the different publisher copyright and self-archiving policies and the ROAR database hosts an index of the repositories themselves.