What is the best way to check the reliability and validity of a resource

The best way to check the reliability and validity of a resource is to look at the authors credentials. Also, was the article or book written in the past ten years? Information changes, the more recent the publication date, the better.

the communist manifesto is an 1848 political pamphlet by the german near the end of the manifesto, the authors call for a "forcible overthrow of all existing social conditions",  ..