In your research you should feel free to cite Wikipedia at will.
If you were footnoting Steffen’s thesis and his dissertation multiple times in the same paper you would need to make the footnotes
distinct by which of the following identifiers?
Which is the correct bibliographic citation for the following website?
What is the correct footnote citation for a website?
Which of the correct bibliographic reference for the dissertation below?
Which of the reference works citations is properly formatted for the bibliography?