We should cite whenever we have directly quoted or paraphrased the work of someone else. You should also cite a source if you are including an image, chart or graph that in not originally yours. In college and always, citing is greatly encouraged whenever you are writing a research paper.
Generally, when a course instructor asks you to not use the Web for your research, this means do not use commonly visited Web sites for your research, however, students may still use online editions of newspapers and articles accessed through article databases. Both newspapers and articles in databases have been checked for factual accuracy. Librarians do suggest to critically examine what may appear to be an online newspaper due to spoof newspaper cites like the Onion. Please clarify database articles or online newspapers with your Instructor before including these resources.
Titles can be misleading. A database can have the word, "full-text" in its title, such as "Medline with Full-text," but that doesn't mean that all the articles that come up in a search result in "Medline" will be full-text. You know you have a full-text article if your see HTML or PDF in the entry on the results page. You can reduce the number of abstracts by selecting the "Full-text" limiter on the database's interface page.
DOI stands for Digital Object Identifier. A DOI can be assigned to any electronic resource as a permanent reference to that "object" or resource. DOIs are unique, meaning that if a DOI is used for one electronic object, it will never be assigned to any other object (similar to a barcode). Because the DOI is unique, it can make a document easy to find and so some citation styles prefer that the DOI is referenced (when available) on the References page.
For information on using DOIs, see the How To Cite in Your Assignments - APA tab