# SABR Model Closed Form Solution

I've been researching the SABR model and one of the main benefits it seems is that you can obtain a closed for solution of the implied BS volatility in certain cases.

In all the papers I've read, I have not found any proofs/reasoning as to where this solution actually comes from.

Does anyone know/can link me to a derivation of it?

This is the formula I am referring to.

Thanks