Reference works make excellent starting points for research; they provide concise articles on key topics by scholars of the field, often accompanied by suggestions for further reading.The following are available online through the Penn Library website.
Vista panoramica desde la Alameda Central. https://commons.wikimedia.org/wiki/Mexico_City_Alameda_Central#/media/File:VISTA_PANORAMICA_DESDE_LA_ALAMEDA_CENTRAL.jpg
Most of the resources listed below are print volumes shelved in the Van Pelt Library Reference Stacks on the first floor of Van Pelt.
Encyclopedia of Mexico by 
Historical Dictionary of Mexico by 
Anuario estadístico de los Estados Unidos Mexicanos
Nuevo atlas nacional de México
Critical Dictionary of Mexican Literature, 1955-2010 by 
Diccionario enciclopédico de música en México by 
Atlas de la diversidad religiosa en México by 
Diccionario de la revolución mexicana by 
Encyclopedia of the Mexican-American War by 
Diccionario Crítico de la Literatura Mexicana, 1955-2005 by 