Ferguson, Henry G. <br/><br/>
United States Geological Survey Bulletin ;   no.580-I 

 - Washington-US :   United States Geological Survey Bulletin,   1914. 
 - páginas 153-182 :   IIustraciones blanco y negro 
 - No. 580-I (1914) 
 - United States Geological Survey Bulletin ;   no.580-I .
 - United States Geological Survey. .