Losada H, Vieyra J, Rangel J, Zamudio A y Martínez G 1997:
The sub-urban agro-ecosystem of maize production in the south-east hills of Mexico City as an important cultural and sustainable crop resource.
Livestock Research for Rural Development. Volume 9, Article #44.
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, from http://www.lrrd.org/lrrd9/5/tito951.htm