Looking for data on minority interest / illiquidity discounts?!

Hey all, I made the mortal sin of agreeing to a post-close seller put, which became available to the original seller on the fifth anniversary of my original acquisition. I’m close to exiting the platform, but the original owner has indicated his desire to exercise his out right preemptively.

does anyone have any research / white paper studies on appropriate discounts for selling a minority interest in a privately held business? This would include typical discounts for minority shareholder, illiquidity, etc.

Greatly appreciate any help,

Michael