Woodruff, E G. <br/><br/>
Oil shale of Northwestern Colorado and Northeastern Utah. 

 - Washington-US :   United States Geological Survey Bulletin,   1914. 
 - páginas 1-21 :   IIustraciones blanco y negro 
 - No. 581-A (1914) 
 - United States Geological Survey Bulletin ;   no.581-A .
 - United States Geological Survey. .