Ponzada, A.C. <br/><br/>
Boletˇn Medusa ;   no. 2 

 - Cleveland-US :   Medusa Portal Cement Company,   1935. 
 - páginas 5-9 
 - Irregular 
 - Vol.5, no. 2(Abr/Jun 1935) 
 - Boletˇn Medusa ;   no. 2 .
 - Medusa Portal Cement Company. .