[1] EГOPИЧEB Г. П.: Интerpaльнoe пpeдcтaвлeниe и вычиcлeниe кoмбинaтopныx cyмм. Haукa, Hoвocибиpcк 1977.
[2] KAUCKY J.: Kombinatoricke identity. Veda, Bratislava 1975
[3] VOSMANSKY J.:
Monotonic properties of zeros and extremants of the differential equations y"+q(t)y 0. Aгch. Math (Brno) 6, 1970, 37-73.
MR 0296420