Thirty-sixth annual meeting of the association of american feographers. 

 - New York-US :   Geografical record,   1940. 
 - páginas 304-308 :   Ilustraciones blanco y negro 
 - Irregular 
 - Vol. XXX, no. 2(Apr. 1940) 
 - The Geographical Review ;   no. 2 .
 - The Geographical Review. .