Google Scholar allows users to search for digital or physical copies of articles, whether online or in libraries Google Scholar is relatively quick and easy to use. “Scholarly” searches will appear using the references from “’full-text journal articles, technical reports, preprints, theses, books, and other documents, including selected Web pages that are deemed to be “scholarly.’” Because most of Google Scholar's search results link directly to commercial journal articles, a majority of the time users will only be able to access a brief summary of the articles topics, as well as small amounts of important information regarding the article, and possibly have to pay a fee to access the entire article. Google Scholar is as easy to use as with the regular Google web search, especially with the helpfulness of the "advanced search" option, which can automatically narrow search results to a specific journal or article. The most relevant results for the searched keywords will be listed first, in order of the author's ranking, the number of references that are linked to it and their relevance to other scholarly literature, and the ranking of the publication that the journal appears in. Using its "group of" feature, it shows the available links to journal articles. In the 2005 version, this feature provided a link to both subscription-access versions of an article and to free full-text versions of articles; for most of 2006, it provided links to only the publishers' versions. Since December 2006, it has provided links to both published versions and major open access repositories, but still does not cover those posted on individual faculty web pages;[citation needed] access to such self-archived non-subscription versions is now provided by a link to Google, where one can find such open access articles. Through its "cited by" feature, Google Scholar provides access to abstracts of articles that have cited the article being viewed. It is this feature in particular that provides the citation indexing previously only found in Scopus and Web of Knowledge. Through its "Related articles" feature, Google Scholar presents a list of closely related articles, ranked primarily by how similar these articles are to the original result, but also taking into account the relevance of each paper. Registration not required.