The rarest drug of all. 

 - Nueva York-US :   The Reaerīs Digest Association,   1944. 
 - páginas 77-78:   ilustraciones blanco y negro 
 - Mensual 
 - Vol. 45, no. 269 (Sep. 1944) 
 - The Reader's Digest ;   no. 269 .
 - The Reaerīs Digest Association. .