As with all referencing in academic writing, referencing is a matter of establishing the authority of the source or information you are relying upon as evidence to support the claims you make in your writing. This is the reason for peer review as it is a process that establishes the authority of a work through expert checking. Peer-reviewed published works are accepted as having greater authority than works that are not peer reviewed. Sometimes, however, the most useful research article might not be available as a peer-reviewed published article but it is available to us in an unpublished form. Use other peer-reviewed articles if possible but if there is a lack of published research reports and, for example, a pre-press version is available directly from the author, you may use it. Check whether the article has been published before submitting your final assignment or thesis and, if it has, reference the final version, taking into account any changes that the editors may have required in the peer-review process.
Unpublished and informally published works include:
Author, A. A. (Year). Title of manuscript. Unpublished manuscript [or "manuscript submitted for publication," or "Manuscript in preparation"].
If the unpublished manuscript is from a university, give this information at the end.
If you locate the work on an electronic archive, give this information at the end.
If a URL is available, give it at the end.
If you use a pre-print version of an article that is later published, reference the published version.