Leonid Pavlovych Nizhnik - Yu. M. Berezanskyi; V. I. Horbachuk; M. L. Horbachuk; A. N. Kochubei; S. O. Kuzhel; V. O. Marchenko; V. A. Mykhailets; A. M. Samoilenko; Ye. Ya. Khruslov (Transactions of Institute of Mathematics, the NAS of Ukraine, 2015)