Some examples for literature review searching:
Keywords: marital rape and consent law
Specialized database, such as: GenderWatch
Keywords: sports governing bodies and gymnastics and US
Academic Search Complete (EBSCOhost) search using keywords:
The most recent result about Larry Nasser appeared relevant to the research, but check out the subject terms, or "tags" for this article. Perhaps USA Gymnastics is the sports governing body of interest along with sex crimes. Here's the search redone:
NOTE: It takes multiple searches to get a variety of results/perspectives on your research topic.
Specialty publications, such as Campus Safety, may have related professional articles, not peer-reviewed, such as
Keywords: international gun control
In the US, we call it gun control, but searching for international information, it is usually called "gun policy"
http://GunPolicy.Org looks interesting and is international in scope
RAND's Gun Policy in America includes research on U.S. Gun Policy in a Global Context
Mass Killings in the United States (dates from 2006-2017)
Are there neutral/unbiased sources for my topic?
Check CQ Researcher (the CQ stands for Congressional Quarterly) which produces weekly reports on topics of interest.
Every reports contains
Pros/Cons will help you see the topic from a number of different perspectives.