Boletˇn Medusa ;   no. 1 

 - Cleveland-US :   Medusa Portal Cement Company,   1936. 
 - páginas 8-9 
 - Irregular 
 - Vol. 6, no. 1(Ene/Abr 1936) 
 - Boletˇn Medusa ;   no. 1 .
 - Medusa Portal Cement Company. .