Check that your sources are valid the easy way by answering these questions:
- WHO: Who wrote/created this source?
- WHAT: What are the author's motivations in creating this source? Are they academic or opinionated?
- WHERE: Where are the cited sources in the bibliography from? Do they appear reliable?
- WHEN: When did they create this source? Have there been advances since then?
- WHY: Why is the author qualified discuss this subject?
- HOW: How did you find this source? Did you use a database?
Peer-reviewed sources are also generally reliable, but you should always make your own intelligent evaluation of a source before you take it as fact!