ISBN 0-931462-20-7* "The United States Correspondence Chess Championship" by Yakov Estrin, Correspondence Chess League of America (1978)* "Wilkes-Barre Variation, Two Knights Defense" by Yakov Estrin, Chess Enterprises (June 1978).
ISBN 0-931462-20-7* The United States Correspondence Chess Championship, Correspondence Chess League of America (1978)* Wilkes-Barre Variation, Two Knights Defense, Chess Enterprises (June 1978).