High Quality Content by WIKIPEDIA articles! Sergei Yakovlevich Efron (Russian: Сергей Яковлевич Эфрон) (8 October 1893, Moscow - 16 October 1941), nicknamed Seryozha, was Russian poet, officer of White Army and husband of Marina Tsvetaeva. While in emigration, he was recruited by the Soviet secret police NKVD. After returning to Russia from France he was executed.