In an author's note in "The Ringworld Engineers", Larry Niven stated that he was finished writing stories in the "Known Space" universe, and that "f you want more "Known Space" stories, you'll have to write them yourself." Internet writer Elf Sternberg took him up on that offer, penning a parody in which members of Niven's hyper-masculine Kzin species engage in gay sex and BDSM. Niven responded by denouncing Sternberg's story in the introduction to "Man-Kzin Wars IV" (Baen Books, 1991) and issuing a cease-and-desist for copyright violation. To date, Sternberg holds that the story is constitutionally protected parody, while Niven maintains that it is a copyright violation that lies outside of protected speech, though he has not legally pursued the matter further.