Isaac Yefremovich Boleslavsky was a Soviet chess player and writer.
Isaac Boleslavsky
Mikhail Moiseyevich Botvinnik was a Soviet and Russian chess grandmaster who held five world titles in three different reigns. The sixth World Chess Champion, he also worked as an electrical engineer and computer scientist and was a pioneer in computer chess. He also had a mathematics degree (honorary).
Botvinnik in 1962
Botvinnik in 1927
Botvinnik vs. Lasker, 1936
Levenfish vs. Botvinnik (right), 1937