Professor of Moscow University, 1918. Head of the Department of the History of Books at the Historical Museum, Moscow, 1919-1941. Worked at the Moscow Gorkii Institute of World Literature of the Academy of Sciences, 1935-1953.
From 1900 published some 300 works, including Russkaia Lirika, 1914, Pesni Russkikh Poetov, 1936 and Russkie Pesni 19-go Veka, 1944. His private library and collection of Russian poetry was unique. After his death, it was given to the Pushkin Museum, Moscow.