I have been trying to understand how to price FX options with barriers. In Hull (Options, Futures, and Other Derivatives), there are closed formulas how to calculate the premiums of European Call and Put options with barriers. However, I am not able to find either closed formula or a model of computing the price of FX options with American barriers. I am not experienced with pricing of FX options, so I apologise if that seems to be an elementary question.
Could anyone please advise where I can read or find more information?
Thank you in advance!