What is the publisher of XXX?
Pebble in the Sky
Pebble in the Sky was also included in a number of omnibuses: first in 1952 in Triangle along with the others in the Empire series (The Stars, Like Dust and The Currents of Space which had only been published earlier that year), in 1978 in The Far Ends of Time and Earth along with The End of Eternity and the short story collection Earth Is Room Enough, and again with the Empire series novels in 2002 as The Empire Novels.