Your literature review should be as comprehensive as possible -- you want to include all of the relevant resources dealing with your topic. Missing important articles or researchers will significantly weaken your scholarship! So, searching comprehensively becomes important.
To ensuring comprehensiveness:
Using a multi-database search (such as Thoreau) is not necessarily recommended; in doing so, you lose the ability to use subject terms and search limits that may be unique to each database.
These can all be important sources of statistics and reliable information. These will not be peer-reviewed resources (i.e. since they are not journals, they do not employ the same sort of editorial process that results in peer-review). Evaluating for reliability is important!
Google Scholar provides a good way to take your search beyond the databases; it searches very broadly and will pull in resources you may not have discovered before.
Google's definition of scholarly includes government sites, think tanks, research organizations, journal websites, and of course colleges and universities.
Unfortunately, there is no way to limit your Google Scholar search to only peer-reviewed resources -- so, you will need to invest time and skill in evaluating the resource, before deciding if it's something that can be included.
The standards for scholarly rigor set in the rubric require you to focus your research in the scholarly (i.e. peer-reviewed) journals, most of which are found in our research databases. Discover databases in your field of study on our Articles by Topic page.
Being able to verify that a resource is peer-reviewed is very important as it helps to show you are meeting scholarly rigor.
The most reliable way is to verify peer-review is to look up the journal in Ulrich's Periodical's Directory.
Ulrich's can tell you, authoritatively, if the journal follows a peer-reviewed (or "refereed") editorial process.
Simply search for the journal's title on Ulrich's search page, and then find your journal in the list of results. If the referee jersey icon is shown, then the journal is refereed!
Ulrich's also contains other information about journals, such as where they are published, names of the editorial staff, etc.
Finding dissertations and doctoral studies can be useful. While these are not peer-reviewed resources, they are valuable sources of information and citations that can inform your own work.
The literature review process is an iterative one. In this process you will: