In this paper we study properties of symbols such that these belong to class of symbols sitting inside that we shall introduce as the following. So for because hypoelliptic pseudodifferential operators play a key role in quantum mechanics we will investigate some properties of −hypoelliptic pseudo differential operators for which define base on this class of symbols. Also we consider maximal and minimal operators of -hypoelliptic pseudo differential operators and we express some results about these operators.
