La Ohia Bell telephone compañia. 

 - Cleveland-US :   Medusa Portal Cement Company,   1931. 
 - páginas 5-6 
 - Irregular 
 - Vol. 2, no. 9(Oct. 1931) 
 - Bolet¡n Medusa ;   no. 9 .
 - Medusa Portal Cement Company. .