I got for a review one Master thesis in the field of computer science. The student mostly uses internet blogs and some lecture slides found on Internet as a source of information. This is a bit of surprise for me because in natural sciences we do not trust such sources. Typically one needs to cite a paper or a book. But I am not sure about computer sciences: what is the standard in this field?
Edit in response to a question:
In order to explain R² in Statistics the student uses this blog.
In my opinion this is a rather standard stuff and some good book should be cited instead. Moreover, this suggests that the student avoids reading books.