Alexander Kronrod
Aleksandr (Alexander) Semenovich Kronrod (Russian: Алекса́ндр Семёнович Кронро́д ) (October 22, 1921 – October 6, 1986) was a Soviet mathematician and computer scientist, best known for the Gauss-Kronrod quadrature formula which he published in 1964.
 Earlier, he worked on computational solutions of problems emerging in theoretical physics.
 He is also known for his contributions to economics, specifically for proposing corrections and calculating price formation for the USSR.
 Later, Kronrod gave his fortune and life to medicine to care for terminal cancer patients.
 Kronrod is remembered for his captivating personality and was admired as a student, teacher and leader.
Christ–Kiselev maximal inequality
In mathematics, the Christ–Kiselev maximal inequality is a maximal inequality for filtrations, named for mathematicians Michael Christ and Alexander Kiselev.
Ostrowski–Hadamard gap theorem
In mathematics, the Ostrowski–Hadamard gap theorem is a result about the analytic continuation of complex power series whose non-zero terms are of orders that have a suitable "gap" between them.
 Such a power series is "badly behaved" in the sense that it cannot be extended to be an analytic function anywhere on the boundary of its disc of convergence.
 The result is named after the mathematicians Alexander Ostrowski and Jacques Hadamard.
Alexander Aigner
Alexander Aigner (* 18 May 1909 in Graz, † 1988) was a full university professor for mathematics at the Karl Franzens University in Graz, Austria.
 During World War II he was part of a group of five mathematicians, which was recruited by the military cryptanalyst Wilhelm Fenner, and which included Ernst Witt, Georg Aumann, Oswald Teichmueller and Johann Friedrich Schultze, to form the backbone of the new mathematical research department in the late 1930s, which would eventually be called Section IVc of Cipher Department of the High Command of the Wehrmacht.
 (abbr.
 OKW/Chi).
 The group was led by the German professor of mathematics Wolfgang Franz.
Alexander Aitken
Alexander Craig "Alec" Aitken (1 April 1895 – 3 November 1967) was one of New Zealand's greatest mathematicians.
 In a 1935 paper he introduced the concept of generalized least squares, along with now standard vector/matrix notation for the linear regression model.
 Another influential paper co-authored with his student Harold Silverstone established the lower bound on the variance of an estimator, now known as Cramér–Rao bound.
Wolfgang Franz (mathematician)
Wolfgang Franz (born October 4, 1905 in Magdeburg, Germany; died April 26, 1996) was a German mathematician who specialized in topology particularly in 3-manifolds, which he generalized to higher dimensions.
 He is known for the Reidemeister–Franz torsion.
 He also made important contributions to the theory of Lens space.
 During World War II he led a group of five mathematicians, recruited by Wilhelm Fenner, and which included Ernst Witt, Georg Aumann, Alexander Aigner, Oswald Teichmueller and Johann Friedrich Schultze, to form the backbone of the new mathematical research department in the late 1930's, which would eventually be called: Section IVc of Cipher Department of the High Command of the Wehrmacht (abbr.
 OKW/Chi).
Greek mathematics
Greek mathematics is the mathematics written by Greek mathematicians, developed from the 7th century BC to the 4th century AD around the shores of the Eastern Mediterranean.
 Greek mathematicians lived in cities spread over the entire Eastern Mediterranean from Italy to North Africa but were united by culture and language.
 Greek mathematics of the period following Alexander the Great is sometimes called Hellenistic mathematics.
 The word "mathematics" itself derives from the ancient Greek "μάθημα" ("mathema"), meaning "subject of instruction".
 The study of mathematics for its own sake and the use of generalized mathematical theories and proofs is the key difference between Greek mathematics and those of preceding civilizations.
Georg Aumann
Georg Aumann (November 11, 1906, Munich, Germany – August 4, 1980), was a German mathematician.
 He was known for his work in general topology and regulated functions.
 During World War II, he worked as part of a group of five mathematicians, recruited by Wilhelm Fenner, and which included Ernst Witt, Georg Aumann, Alexander Aigner, Oswald Teichmueller and Johann Friedrich Schultze, and lead by Wolfgang Franz, to form the backbone of the new mathematical mathematical research department in the late 1930's, which would eventually be called: Section IVc of Cipher Department of the High Command of the Wehrmacht (abbr.
 OKW/Chi).
 He also worked as a cryptanalyst, on the initial breaking of the most difficult cyphers.
 He was also involved in the development of cryptanalytic theory.
Quaternion Society
A scientific society, the Quaternion Society was an "International Association for Promoting the Study of Quaternions and Allied Systems of Mathematics".
 At its peak it consisted of about 60 mathematicians spread throughout the academic world that were experimenting with quaternions and other hypercomplex number systems.
 The guiding light was Alexander Macfarlane who served as its Secretary initially, and became President in 1909.
 The Association published a "Bibliography" in 1904 and a "Bulletin" (annual report) from 1900 to 1913.

Question: Were both Alexander Kronrod and Leonty Magnitsky mathematicians?
Answer: yes