WAHLSTROM, Ernest E. <br/><br/>
History of geologic investigations, engineering design, and construction methods of the Harold D. Roberts Tunnel, Colorado / 
by Ernest E. Wahlstrom. 
 -- Washington :   United States Government Printing Office,   1974 
 - 13 p. + map. -- 
 (Geological Survey Professional Paper  ;  831-A).
<br/><br/><label>Subjects--Topical Terms: </label><br/>Colorado<br/>Geología
<br/><br/><label>Universal Decimal Class. No.: </label>55(788)