> The best depth before you hit the knee in the curve is undergraduate-level textbooks. That matches my experience as well. Having graduated from two fields at

> The best depth before you hit the knee in the curve is undergraduate-level textbooks. That matches my experience as well. Having graduated from two fields at university, the most foundational knowledge came in the first two years. The third one is a deepening of the first two but can be skipped if only basis are needed. Then master degree is just playing with higher level concepts and linguo.