Encyclopedia of Agrochemicals, 3 Volume Set [Knovel]. Wiley-Interscience [Imprint] Dec. 2002 Hoboken : John Wiley & Sons, Incorporated [2002].
Encyclopedia of organic, sustainable, and local food [ebrary] / edited by Leslie A. Duram. Santa Barbara, Calif. : Greenwood, c2010.
Urban Agriculture: A Literature Review - Urban Agriculture: Differing Phenomena in Differing Regions of the World / Charlie W. Lesher, Jr. USDA, NAL, Autumn 2006 [download the 96 page pdf]
The following are free indexes - no subscription needed.
Urban Agriculture Notes by City Farmer - Canada's Office of Urban Agriculture [former site: http://www.cityfarmer.org/]
Urban Agriculture, Alternative Farming Systems Information Center (AFSIC) - USDA