A simple functional operator. Risteski, Ice B.; Trenčevski, Kostadin G.; Covachev, Valéry C. — 1999 The New York Journal of Mathematics [electronic only]
Cyclic complex vector functional equations. Risteski, Ice B.; Trenčevski, Kostadin G.; Covachev, Valéry C. — 2000 APPS. Applied Sciences
Some complex vector systems of partial functional equations Ice B. Risteski; Kostadin G. Trenčevski; Valéry C. Covachev — 2003 Archivum Mathematicum In this paper some types of complex vector systems of partial linear and non-linear functional equations are solved.