Graham, Ian. <br/><br/>
Across the petén to the ruins of machaquilá. 

 - Pennsilvania-US :   Univesity of Pennsylvania,   1963. 
 - páginas 2-10 :   ilustraciones blanco y negro 
 - Trimenstral 
 - Vol.5, no4 (1963)  
 - Expedition. the bulletin of the university museum of the university of pennsilvania ;   no. 4 .
 - University of Pennsylvania. .