00448naa#a2200169#i#450# EN\INFRA-M\bibl\271 20241212163418.4 2308-4898 20130603b2013####ek#y0engy0150####ca RUS RU Ellipse: tangent and normal Journal article Moscow INFRA-M Academic Publishing LLC. 2013 2 с. Journal article local Sal'kov N. A. naukaru.ru