The following youtube videos will help explain the components of a literature review.
A DOI is a Digital Object Identifier.
It is a unique alphanumeric string assigned by a registration agency (the International DOI Foundation) to identify content and provide a persistent link to its location on the Internet. The publisher assigns a DOI when your article is published and made available electronically.
All DOI numbers begin with a 10 and contain a prefix and a suffix separated by a slash. The prefix is a unique number of four or more digits assigned to organizations; the suffix is assigned by the publisher and was designed to be flexible with publisher identification standards.
American Psychological Association. (2013). What is a digital object identifier, or DOI?. Retrieved from http://www.apastyle.org/learn/faqs/what-is-doi.aspx
If you don't see one and want to check, you can go to crossref.org and type in the author's last name and the name of the journal article.
If a DOI is available, you will need to add it to your citation.
Karplus, M. (2010). Dynamical aspects of molecular recognition. Journal of Molecular Recognition, 23(2), 102-104. doi: 10.1002/jmr.1018
If the article does not have a DOI, then you would cite your article with the url of the journal home page.
If you found the article in a database and it is only published in that database, then you can add the database name and accession number or the database URL
Berman, R. P. (2009). Fused voices: Narrated monologue in jane austen's emma. Nineteenth-Century Literature, 64(1), 1-15. Retrieved from http://ucpressjournals.com/journal.php?j=ncl
Bilger, A.(2009). Women Novelists Before Jane Austen: The Critics and Their Canons (review). Tulsa Studies in Women's Literature 28(1), 201-202. The University of Tulsa. Retrieved October 9, 2013, from Project MUSE database.