Boletˇn Medusa ;   no. 3 

 - Cleveland-US :   Medusa Portal Cement Company,   1935. 
 - páginas 6-8 
 - Irregular 
 - Vol.5, no. 3(Jul/Sep 1935) 
 - Boletˇn Medusa ;   no. 3 .
 - Medusa Portal Cement Company. .