My best friend is older mathematician is his late 70's. His best friend,Вадим Могильницкий, who unfortunately passed away, was an avid collectors of Richter's audio recordings and Richter's biographer. He published two books: "Святослав Рихтер" (S. Richter) and "Рихтер - Ансамблист" (Richer - Ansamblyst). They were never translated to English.