In 1951, a science fiction book titled "The Case of the Little Green Men" was published by Mack Reynolds, telling of a private detective hired to investigate disguised aliens living among the human population. As he was being hired, the detective referred derisively and familiarly to the aliens in the flying saucers being "little green men". The cover illustration is notable for depicting the LGM with the classic antennae sticking out of the head. Mack Reynolds would go on to write the first "Star Trek" novel in 1968 ("Mission to Horatius").