Pfeiffer, Heorhii or Georgii or Yurii [Пфейффер, Георгій; Pfejffer, Heorhij], b 23 December 1872 in Sokyryntsi, Pryluky county, Poltava gubernia, d 10 October 1946 in Kyiv. Mathematician; full member of the All-Ukrainian Academy of Sciences (VUAN) from 1920. After graduating from Kyiv University in 1896, he taught at Kyiv Polytechnical Institute (1899–1909) and at Kyiv University (1900–46). He served as chairman of the VUAN Commission on Pure Mathematics (from 1920), research associate of the Institute of Mathematics of the Academy of Sciences of the Ukrainian SSR in Kyiv (1934–41, 1944–6), and director of the (combined) Institute of Mathematics and Physics in Ufa (1941–4). Pfeiffer made significant contributions to the theory of partial differential equations (PDEs) and to the theory of Lie and Lagrange integrals. Among his many contributions to mathematics is a general method for the formal integration of nonlinear equations and complete systems of nonlinear PDEs of the first order.
[This article originally appeared in the Encyclopedia of Ukraine, vol. 3 (1993).]