Geological survey research 1961 / 
Director Thomas B. Nolan. 
 -- Washington :   United States Government Printing Office,   1961 
 - 194 p. -- 
 (Geological Survey Professional Paper  ;  424-A).
<br/><br/><label>Subjects--Topical Terms: </label><br/>Geología
<br/><br/><label>Universal Decimal Class. No.: </label>55