Here a book chapter I published with Professor Antonio Serratos "Redefining the rural-urban relationship through multifunctional peri-urban agriculture: The case of native maize conservation in Mexico City", in Pillarisetti, R., Lawrey Roger and Ahmad Azman (eds) Multifunctional Agriculture, Ecology and Food Security: International Perspectives, edited by Nova Science, New York. 
It's available in Amazon http://www.amazon.ca/Multifunctional-Agriculture-Ecology-Food-Security/dp/1626182949