MathSciNet provides abstracts, bibliographic information, and reviews of mathematical literature. Review articles published in Mathematical Reviews are written by expert reviewers selected by staff mathematicians. In addition to the review articles, MathSciNet also contains direct links to original articles.
JSTOR is collection of core scholarly journals, many going back to the first volume. Emphasis is on back issue coverage and does not include the current 3-5 years, unless Gordon has a current subscription to the journal. JSTOR provides long term preservation for journals.
The building block of a library database search is keywords. Keywords are central ideas or terms within your research question or problem.
Once you have your keywords identified (2-3 is a good place to begin), you then need to connect them together in a way the database understands how to search. This is done using the Boolean search operators AND, OR, and NOT. Connecting keywords using these search operators creates a search string.
Do not limit your search to just one database. Instead look at a variety of databases both subject specific and interdisciplinary to make sure you are viewing the full scope of literature published on your topic.