Hancock, E T. <br/><br/>
United States Geological Survey Bulletin ;   no.716-C 

 - Washington-US :   United States Geological Survey Bulletin,   1918. 
 - páginas 35-53 :   IIustraciones blanco y negro 
 - No. 716-C (1920) 
 - United States Geological Survey Bulletin ;   no.716-C .
 - United States Geological Survey. .