1.
Ivanov V. ON LOWER BOUNDS OF THE SECOND-ORDER DINI DIRECTIONAL DERIVATIVES. Ann. Sofia Univ. Fac. Math. and Inf. [Internet]. 2004 Dec. 12 [cited 2025 Jan. 15];96:163-71. Available from: https://admin.uni-sofia.bg/index.php/fmi/article/view/170