KorolyukV.S., LukovskyI.O., PerestyukN.A., PratsiovytyiM.V., SamoilenkoA.M. and YakovetsV.P. 2012. Mykola Ivanovych Shkil’ (on his 80th birthday). Ukrains’kyi Matematychnyi Zhurnal. 64, 12 (Dec. 2012), 1720-1722.