Green Open Access materials are peer-reviewed articles that are made available in free repositories. In this process, the author self-archives his or her article.
Gold Open Access materials are articles published in open access journals where they are made freely available to read. Some gold access journals charge a fee to authors in order to publish.
Open access, peer-reviewed journals can be difficult to locate. Since open access journals can be of varying quality, listed below are some sites that evaluate and index open access journals. Resources are also listed to assist in assessing open access journals.