Validator implementation tips?

Question

css

Greetings.
As part of the university master's work, the task is to study the process of validating the source code (in this case, it is html and css, for now) and implementing the validator.
So, I would like to know the opinion and advice of people who have faced such tasks, namely to find out:

1. Recommended languages ​​for implementation
   
2. Recommended software, services, etc.
   
3. Literature and sources
   

Thanks in advance!

Answer 1

I think it will not be superfluous
3. https://github.com/CSSLint/csslint/wiki

Answer 2

1. Perl or Python.
2. validator.w3.org
3. if in Russian, then here - htmlbook.ru