some of his students' students. Several of them became his co-authors: V. Berestovskii, A. Verner, N. Netsvetaev, I. Nikolaev, and V. Ryzhik. His last Ph.D. student was Grigori Perelman who proved Thurston's geometrization conjecture in 2002/2003 which contains the Poincaré conjecture as a special case. Mountaineering Aleksandrov became attracted to alpinism under the influence of his advisor Boris Delaunay. In the summer of 1937, after defending his D.Sc., …together with I. Chashnikov he makes a first climb to the Chotchi summit, and with K. Piskaryov performs a climb of Bu-Ul'gen via the western wall (one of the first wall climbs in the history of the Soviet alpinism).[…] In 1940 he participates in a record-making traversal[…] He manages, almost by a miracle, to stop the fall of A. Gromov, who had fallen along with a snow shelf. It was with this traversal that Aleksandrov completed the alpinist sports master requirements. The German-Soviet War postponed awarding him this honorary title until 1949. During his rectorship, Aleksandrov also advanced the mountaineering sport activities in the university, actively participating in the climbs. The fiftieth birthday was celebrated by Aleksandrov in the mountains with his friends. On that day he made a solo first climb of an …unnamed peak 6222 m (Shakhdarinsk ridge, Pamir), that as he suggested was then named "The peak of the Leningrad university." During later years Aleksandrov was unable to climb due to health problems, yet he never ceased dreaming of climbing. Finally, in 1982, the year of his seventieth birthday, he, together with K. Tolstov, performed in Tian Shan his last climb, of the Panfilov Peak… See also CAT(k) space Cauchy's theorem Alexandrov theorem Aleksandrov–Rassias problem Alexandrov–Fenchel inequality Alexandrov's uniqueness theorem Alexandrov’s soap bubble theorem References Академик Александр Данилович Александров. Воспоминания. Публикации. Материалы. (Academician Aleksandr Danilovich Aleksandrov. Recollections. Publications. Biographical materials, in Russian). Editors: G.M. Idlis and O.A. Ladyzhenskaya. Moscow, Nauka publishing house, 2002. Yu. F. Borisov, "On the 90th anniversary of the birth of A.D. Aleksandrov (1912–1999)", Russ. Math. Surv., 2002, 57 (5), 1017–1031. Yu. F. Borisov, V.A. Zalgaller, Kutateladze, S.S., O.A. Ladyzhenskaya, A.V. Pogorelov, Yu. G. Reshetnyak, "К 90-летию со дня рождения А.Д. Александрова (1912–1999)", Uspekhi Mat. Nauk, 2002, 57 (5), 169–181. Liyun Tan and Shuhuang Xiang, On the Aleksandrov-Rassias problem and the Hyers-Ulam-Rassias stability problem, Banach Journal of Mathematical Analysis, 1(1)(2007), 11–22. A.M. Vershik, "Alexander Danilovich as I knew him (in Russian).", St. Petersburg University, No. 3-4