In academic work one sometimes encounters cites without page numbers (e.g., Gurr 1970) and other times with them (e.g., Gurr 1970, pp. 61-3). How does an author decide which is appropriate?
The rule is simple. If the claim you are citing is the major point of that work, then omit a page reference. Why? Because there is no single page number that it would make sense to reference. If, however, the reference is to a point other than the major point of that work, then it is important to include the page number(s) so that readers can know where in that work to find the claim you ate citing.