In a recent paper [11], R.E. Curto, S.H. Lee and J. Yoon asked the following question. Let A be subnormal operator, assume that A2 is quasinormal. Does it follow quasinormal? this paper, we answer question in affirmative. fact, prove more general result nth roots of quasinormal operators are Research on problem has led us to new criterion for semispectral measure half-line spectral, written ter...

-Some new oscillation criteria for the even order damped functional differential equation (a(t)z(n-1)(t)) ' ÷ p(t)lz(n-1)(Ol#x(n-a)(O ÷ q(t)f(xIaa(t)] . . . . . =Lq.~(t)]) = 0 are established, where ~ _> O. These criteria are an extension of some of the known results. 1. I N T R O D U C T I O N Recently, Grace and Lalli [1] discussed the oscillation of the nth-order functional differential equa...