Coe, Sophie D. America's first cuisines. University of Texas Press, 1994.
Coe, Sophie D. and Michael D. Coe. The true history of chocolate. 2nd edition. Thames and Hudson, 2007.
Diccionario enciclopedico de gastronomia mexicana. 6. burrito-calabacitas con queso. Clio, 200-?
Young, Allen M. The chocolate tree : a natural history of cacao. Rev. and expanded ed. University Press of Florida, 2007.
My apologies for not putting citations in the correct format, will update and correct later.