Letter Request to be an official opponent at V.N. Lifshits’s thesis defending; short account of the work’s history and of interaction with A.A. Liapunov. Date: 12.08.1973 Original document language: russian Authors: Leonid E. Sadovsky Persons: Alexei A. Lyapunov, Vladimir N. Lifshits Addressee: Andrei Petrovich Ershov
