Thus, when Robert Heinlein had written about a "generation ship" (a slower than light multi-generation interstellar spaceship), then so did Poul Anderson, Brian Aldiss and Clifford Simak. Aldiss even said, in a conversation at Eastercon 1970, "I thought I could do it better!"
Much later, collaboration was institutionalized:
"The franchise universe lives!"
-Larry Niven, Man-Kzin Wars II (London, 1991), p. vii.
Now, Poul Anderson, Jerry Pournelle, SM Stirling and others were able not only to write about militaristic, carnivorous, feline aliens but also to call them kzinti. Anderson's Man-Kzin Wars stories are:
"Iron" (also here, here and here)
"Inconstant Star" (also here, here, here, here and here);
"Pele" (also here).
We have been following Jerry Pournelle and SM Stirling as to some extent successors of Poul Anderson so we might be interested in rereading their co-written Man-Kzin Wars stories. Since the first of these, "The Children's Hour," is 171 pages long, I regard it as a novel.