00468naa#a2200169#i#450# EN\INFRA-M\bibl\11982 20251210212943.3 2308-4898 20160618b2016####ek#y0engy0150####ca RUS RU Dupin Cyclide and Second-Order Curves. Part 1 Journal article Moscow INFRA-M Academic Publishing LLC. 2016 9 с. Journal article local Sal'kov N. A. naukaru.ru