Evgenii Mikhailovich Landis (, Yevgeny Mikhaylovich Landis; 6 October 1921 – 12 December 1997) was a Soviet mathematician who worked mainly on partial differential equations. Life Landis was born in Kharkiv, Ukrainian SSR, Soviet Union. He was Jewish. He studied and worked at the Moscow State University, where his advisor was Alexander Kronrod, and later Ivan Petrovsky. In 1946, together with Kronrod, he rediscovered Sard's lemma, unknown in USSR at the time. Later, he worked on uniqueness theorems for elliptic and parabolic differential equations, Harnack inequalities, and Phragmén–Lindelöf type theorems. With Georgy Adelson-Velsky, he invented the AVL tree data structure (where "AVL" stands for Adelson-Velsky Landis). He died in Moscow. His students include Yulij Ilyashenko. External links Biography of Y.M. Landis at the International Centre for Mathematical Sciences. 20th-century Russian mathematicians Soviet mathematicians Soviet inventors Moscow State University alumni 1921 births 1997 deaths Mathematical analysts Ukrainian Jews Ukrainian mathematicians Ukrainian inventors