Poul Anderson <br/><br/>
The Shield of Time 

 -  Tor Books 
 - 448 pages 
<br/><br/> Manse Everard is a man with a mission. As an Unattached Agent of the Time Patrol, he's to go anyplace - and anytime! - where humanity's transcendent future is threatened by the alteration of the past. This is Manse's profession, and his burden: for how much suffering, throughout human history, can he bear to preserve? 
<br/><br/><label>ISBN: </label>9780812510003 
<br/><br/><label>Standard No.: </label>23981002 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Science Fiction
<br/><br/><label>LC Class. No.: </label>PS3551.N378 
<br/><br/><label>Dewey Class. No.: </label>813.54