Howykowycz, Mariya     Construction of invariant difference and discrete analogues of differential operators of hogh order dicretization error [Текст] / Mariya Howykowycz // Computational problems of electrical engineeringVol. 2. Vol. 2. N. 1 ; Lviv Polytechnic Nat. Univ. ; ed.-in-chief Yuriy Bobalo - Lviv : Lviv Polytechnic nat. univ. , 2012. — P. 37-40.