Which mathematician was the father of physicist Nikolai Borisovich Delone: Jakow Trachtenberg or Boris Delaunay?
Jakow Trachtenberg Jakow Trachtenberg (17 June 1888 – 1953) was a Jewish mathematician who developed the mental calculation techniques called the Trachtenberg system.
Julian Sochocki Julian Karol Sochocki (Russian: Юлиан Карл Васильевич Сохоцкий , Polish: "Julian Karol Sochocki" ; February 2, 1842 in Warsaw, Congress Poland, Russian Empire – December 14, 1927 in Leningrad, Soviet Union) was a Russian-Polish mathematician. His name is sometimes transliterated from Russian in several different ways (e.g. Sokhotski or Sochotski).