All resources utilized in research should be evaluated for credibility. This includes: books, journal articles, websites, photographs, newspapers, videos, and more. Question everything.
Ask questions such as:
Who wrote it?
Who published it?
Where does the information come from? What sources does the resource cite?
Does the resource seem to have a bias?
How old is the resource?
Are there good reviews of the resource?
Will my audience accept this resources as reliable?