IR skew
https://lesniewski.us/papers/lectures/Interest_Rate_and_FX_Models_NYU_2013/Lecture6_2013.pdf
https://mfe.baruch.cuny.edu/wp-content/uploads/2015/06/VolWork1-Andrew.pdf
Longstaff-Schwartz https://people.math.ethz.ch/~hjfurrer/teaching/LongstaffSchwartzAmericanOptionsLeastSquareMonteCarlo.pdf
https://kth.diva-portal.org/smash/get/diva2:1221305/FULLTEXT01.pdf