Question: Who was known for interpolation, Nikolay Mitrofanovich Krylov or Leonty Magnitsky?
Context: The Krylov–Bogolyubov averaging method (Krylov–Bogolyubov method of averaging) is a mathematical method for approximate analysis of oscillating processes in non-linear mechanics.  The method is based on the averaging principle when the exact differential equation of the motion is replaced by its averaged version.  The method is named after Nikolay Krylov and Nikolay Bogoliubov. Nikolay Sergeevich Krylov (Russian: Никола́й Серге́евич Крыло́в }; 10 August 1917 – 21 June 1947) was a Russian theoretical physicist known for his work on the foundations of statistical physics.  He showed that a sufficient condition for a dynamical system to relax to equilibrium is for it to be mixing. The Magnitsky Act, formally known as the Russia and Moldova Jackson–Vanik Repeal and Sergei Magnitsky Rule of Law Accountability Act of 2012, is a bipartisan bill passed by the U.S. Congress and signed by President Obama in November–December 2012, intending to punish Russian officials responsible for the death of Russian tax accountant Sergei Magnitsky in a Moscow prison in 2009. Cape Yevgenov ( ) is an ice-covered cape midway along the northeast side of Krylov Peninsula, forming the west entrance to Lauritzen Bay, Antarctica.  Photographed by U.S. Navy Operation Highjump (1946–47), Soviet Antarctic Expedition (1957–58), and ANARE (Australian National Antarctic Research Expeditions) (1959).  Named by Soviet Antarctic Expedition after Russian hydrographer Nikolay I. Yevgenov (1888–1964). Nikolay Mitrofanovich Krylov (Russian: Никола́й Митрофа́нович Крыло́в , Ukrainian: Микола Митрофанович Крилов ) (29 November [O.S. 17 November] 1879 – May 11, 1955) was a Russian and Soviet mathematician known for works on interpolation, non-linear mechanics, and numerical methods for solving equations of mathematical physics. In control systems theory, the describing function (DF) method, developed by Nikolay Mitrofanovich Krylov and Nikolay Bogoliubov in the 1930s, and extended by Ralph Kochenburger is an approximate procedure for analyzing certain nonlinear control problems.  It is based on quasi-linearization, which is the approximation of the non-linear system under investigation by a linear time-invariant (LTI) transfer function that depends on the amplitude of the input waveform.  By definition, a transfer function of a true LTI system cannot depend on the amplitude of the input function because an LTI system is linear.  Thus, this dependence on amplitude generates a family of linear systems that are combined in an attempt to capture salient features of the non-linear system behavior.  The describing function is one of the few widely applicable methods for designing nonlinear systems, and is very widely used as a standard mathematical tool for analyzing limit cycles in closed-loop controllers, such as industrial process controls, servomechanisms, and electronic oscillators. Nicolai Vladimirovich Krylov (Russian: Никола́й Влади́мирович Крыло́в ; born 5 June 1941) is a Russian mathematician specializing in partial differential equations, particularly stochastic partial differential equations and diffusion processes.  Krylov studied at Lomonosov University, where he in 1966 under E. B. Dynkin attained a doctoral candidate title (similar to a PhD) and in 1973 a Russian doctoral degree (somewhat more prestigious than a PhD).  He taught from 1966 to 1990 at the Lomonosov University and is since 1990 a professor at the University of Minnesota.  At the beginning of his career (starting from 1963) he, in collaboration with Dynkin, worked on nonlinear stochastic control theory, making advances in the study of convex, nonlinear partial equations of 2nd order ("i.e." Bellman equations), which were examined with stochastic methods.  This led to the Evans-Krylov theory, for which he received with Lawrence C. Evans in 2004 the Leroy P. Steele Prize of the American Mathematical Society (for work done simultaneously and independently by both Krylov and Evans).  They proved the second order differentiability (Hölder continuity of the second derivative) of the solutions of convex, completely nonlinear, second order elliptical partial differential equations and thus the existence of "classical solutions" (Theorem of Evans-Krylov).  He was in 1978 at Helsinki and in 1986 at Berkeley an Invited Speaker for the ICM.  He received the Humboldt Research Award in 2001.  In 1993 he was elected a member of the American Academy of Arts and Sciences (1993).  He should not be confused with the mathematician Nikolay M. Krylov. In mathematics, the Krylov–Bogolyubov theorem (also known as the existence of invariant measures theorem) may refer to either of the two related fundamental theorems within the theory of dynamical systems.  The theorems guarantee the existence of invariant measures for certain "nice" maps defined on "nice" spaces and were named after Russian-Ukrainian mathematicians and theoretical physicists Nikolay Krylov and Nikolay Bogolyubov who proved the theorems. Sergey Mitrofanovich Gorodetsky (Russian: Серге́й Митрофа́нович Городе́цкий ; ] ; January 17 [O.S. January 5] 1884 – June 8, 1967) was a Russian poet, one of the founders (together with Nikolay Gumilev) of "Guild of Poets" ("Цех поэтов").  He was born in Saint Petersburg, and died in Obninsk. Leonty Filippovich Magnitsky (Russian: Леонтий Филиппович Магницкий ), born Telyatin (Russian: Телятин ), (June 9, 1669, Ostashkov – October 19, 1739, Moscow) was a Russian mathematician and educator.
Answer: Nikolay Mitrofanovich Krylov