About 15 years ago, I spent a while on a project to train a language model on a corpus of math, with idea to create a math exploration assistant. The project fo

About 15 years ago, I spent a while on a project to train a language model on a corpus of math, with idea to create a math exploration assistant. The project foundered on my inability extract the typeset math and proofs from print materials into a consistent, machine-readable form. How did OpenAI do it? Don't tell me they OCRed Google Books.