Butler, G. M.  1881- <br/><br/>
Clays of eastern Colorado, 
by G. Montague Butler, 1914. 
 - Denver, Col.,  The Smith-Brooks printing company,  1915. 
 - 353 p.  illus., fold. plans.  24 cm. 
<br/><br/> "Partial list of the sources of data consulted in compiling the descriptions of the Colorado clay-bearing formations": p. 148-149. 
<br/><br/><label>LCCN: </label>gs 15000679  
<br/><br/><label>Subjects--Topical Terms: </label><br/>Clay--Colorado.
<br/><br/><label>LC Class. No.: </label>QE91  / .A4 no.8