Science fiction is a dialogue, a tennis match, in which the Idea is volleyed from one side of the net to the other. Ridiculous to say that someone 'stole' an idea: no, no, a thousand times no. The point is the volley, and how it's carried, and what statement is made by the answering 'statement.' In other words — if Burroughs initiates a time-gate and says it works randomly, and then Norton has time gates confounded with the Perilous Seat, the Siege Perilous of the Round Table, and locates it in a bar on a rainy night — do you see both the humor and the volley in the tennis match?