In this paper we study the Ostrovsky-Hunter equation for the case where the
flux function f(x,u) may depend on the spatial variable with certain
smoothness. Our main results are that if the flux function is smooth enough
(specified later), then there exists a unique entropy solution. To show the
existence, after proving some a priori estimates we have used the method of
compensated compactness and to prove the uniqueness we have employed the method
of doubling of variables