“…The operator T is said to be p-hyponormal, 0`p 1, if T Ã j j 2p T j j 2p X Let H p denote the class of phyponormal operators (so that H 1 denotes the class of 1-hyponormal, or simply hyponormal, operators). Although H p , 0`p`1, contains H 1 as a proper subclass, H p operators have spectral properties very similar to those of H 1 operators (see [1,2,5,6,7,22], and some of the references cited in these papers, for further information on H p operators). It is shown that A B P H p if and only if AY B P H p .…”