sentences:  It was first published in the magazine "Galaxy Science Fiction" for March, 1956, and first appeared in book form in the anthology "The World That Couldn't Be and 8 Other SF Novelets" (Doubleday, 1959).It has since been reprinted in numerous other anthologies, including "The Time Curve" (1968), "3000 Years of Fantasy and Science Fiction" (1972), "Dawn of Time" (1979), "Science Fiction A to Z" (1982), "Grand Masters' Choice" (1989), "Dinosaurs!