For the creative component, and most (if not all) of your courses you are required to use the citation style that is asked of authors that publish articles in one of the journals from the TriSocieties*. Follow the link below, and go to chapter 1 for manuscript publications, to find the rules and requirements for writing citations in that style. I have includes several examples to help you out.
A few highlights: If there are more than three authors, only use the first authors last name/first initial, followed by "et al." If three or less authors, use each authors name as shown below. References are to be listed alphabetically. If you have multiple articles by the same author, use the lettering system to differentiate their order in your list. Within text citations, you should use the authors last name and year... such as this example:
This sentence includes important information that I am going to cite (Smith, 2005).
Also to note, the DOI is not the same thing as a URL. It is similar, in that they are each locations where pages/articles can be found. However, a DOI is more stable, and is the reason why journal articles pretty much always have a DOI for them, not a URL.
A Typical Journal Article Citation, TriSocieties Style Manual:
Author last name, First Initial. Year of Publication. Title of Article. Journal Name using abbreviations. Volume Number: pages. DOI address.
Li, P., J. Chen, and P. Wu. 2011. Agronomic characteristics and grain yield of 30 spring wheat genotypes under drought stress and nonstress conditions. Agron. J. 103:1619–1628. doi:10.2134/agronj2011.0013
P.L Pingali. 2012. Green revolution: Impacts, limits, and the path ahead. Proc. Natl. Acad. Sci. USA 109:12302–12308. doi:10.1073/pnas.0912953109
*The TriSocieties are a combination of 3 professional organizations. Those three organizations are: the American Society of Agronomy, the Crop Science Society of America, and the Soil Science Society of America.