Prometheus Award Winning Author! Here is the finest work of H. Beam Piper (1904-64), an engineer turned science fiction writer. 

Little Fuzzy and Graveyard of Dreams belong to his famous "Terrian Federation" series. 

Time Crime belongs to Piper's tales of various agents of the "Paratime Police" as they work to prevent tyranny and war across the timelines. 

Genesis and Operation RSVP show the author's mind at work outside the confines of either series.