Baker, A.A. <br/><br/>
The northward extension of the sheridan coal field. 

 - Washington-US :   Departament of the Interior,   1929. 
 - páginas 15-67 :   Ilustraciones blanco y negro 
 - Irregular 
 - No. 806 (1929) 
 - Geological Survet. Bulletin ;   no. 806 .
 - United States Goverment Printing Office. .
<br/><br/> Separata.