Shehda, L. M. 2021. “DEGENERATE BOUNDARY-VALUE PROBLEMS WITH A PERTURBING MATRIX FOR A DERIVATIVE: Array”. PRECARPATHIAN BULLETIN OF THE SHEVCHENKO SCIENTIFIC SOCIETY. Number, no. 1(59) (January):29-37. https://doi.org/10.31471/2304-7399-2020-1(59)-29-37.