What were the voting results in those prior referendums?
20 January 1991: Crimea 93.6% to join Russia
16 March 2014: Crimea 96.77% for independence
May 2014: Donetsk 89% for autonomy
May 2014: Lugansk 96% for autonomy
I pulled these numbers from a new book[1], which is in French, but there is already a rough English translation floating around. It is well footnoted with URLs.
[1] https://books.google.com/books/about/Operation_Z.html?id=PYW...
Jacques Baud who wrote that book which you used for the numbers has a history of pushing pro kremlin points and has been on Russian state TV in the past. I wouldn’t consider him reliable on this topic.
If you want to read a good article on Jacques baud the following is a good analysis.
https://dailysceptic.org/archive/how-accurate-is-jacques-bau...
I'm well aware of Baud's writings and his military career. I do have issues with his intellectual honesty, but I think he is in no sense a mouthpiece of Moscow. His driving motivation seems to be not pro-Russia, but anti-USA, which is not so unusual for a Frenchman (Swiss). That article you linked is itself rather dishonest, raising issues and then sidestepping Baud's version of the story.