It is important to be critical of the information you want to use in your thesis, and there are certain things to keep in mind depending on which type of source you are using.
Peer-reviewed journals and well-renowned book publishers have evaluated the quality of the information for you.
But how can you judge other literature you have found on the internet or through the library?
And how can you efficiently select the literature that is relevant for your thesis if your search terms have produced hundreds of results?