The other 10% were books the publisher only had physical prints of or which I could find pdf copies from other locales of.
> LaTeX
I submitted a lot of things done in LaTeX that professors hated grading for the sheer reason that I made them count words manually instead of letting them skim-count based on the number of words on a Word page. I eventually wrangled the `Geometry` and `mla.sty` packages into submission and even made my own custom version of Garamond that added an extra en-space to periods following a character followed by a space just to be boring.
the specific exam I am referring to indicated hand written as a requirement. It's also unlikely that the prof. failing me would have survived the scrutiny of the administration.
Why bother with books when it's so easy to fabricate?
> I once turned in a math exam written using LaTeX and the professor initially declined to grade it.
This is just weird though. I used LaTeX for the majority of my homeworks and also exams. It was about an even split between LaTeX and handwriting for math people iirc.