Natural sciences and mathematics

Wick, K. et al. 2008. Organic Chemistry/Print version. Wikimedia Foundation, San Francisco, California. 20 May 2009.
< http://en.wikibooks.org/wiki/Organic_Chemistry/Print_version >

Weed entertainment

Ekeblad, Eva. 2000-2005. Walks among the S-weeds. Eva Ekeblad, Göteborg, Sweden. 20 May 2009 < http://s-weeds.net >

Online weed keys

NCSU TurfFiles decision aids - Turf and weed ID. 2009. North Carolina State University, Raleigh, NC. 20 May 2009.
< http://www.turffiles.ncsu.edu/turfid/ >

UC guide to healthy lawns - Identification key for weeds in turfgrass. 2009. UC IPM Online, University of California, Davis. 20 May 2009.
< http://www.ipm.ucdavis.edu/TOOLS/TURF/PESTS/beginkey.html >

Weed identification. 2009. College of Agricultural, Consumer and Environmental Sciences, University of Illinois, Urbana. 20 May 2009.
< http://weedid.aces.uiuc.edu >

Weed photo galleries

Anonymous. 2008. Plant photogallery: Plants by scientific name. Center for Aquatic and Invasive Plants, University of Florida, Gainesville. 20 May 2009.
< http://plants.ifas.ufl.edu/photos.html >

Anonymous. 2008. Photo gallery. Weed Science Society of America, PO Box 7050 Lawrence, KS 66044-8897 USA. 20 May 2009.
< http://www.wssa.net/Weeds/ID/PhotoGallery.htm >

Randall, R. P. 2007. Global compendium of weeds. Hawaiian Ecosystems at Risk Project, Botany Department, University of Hawaii. 20 May 2009.
< http://www.hear.org/gcw/ >

USDA, NRCS. 2009. The PLANTS database image gallery. National Plant Data Center, Natural Resources Conservation Service, United States Department of Agriculture, Baton Rouge, LA 70874-4490 USA. 20 May 2009.

< http://plants.usda.gov/gallery.html >

Wunderlin, R. P., and B. F. Hansen. 2008. ISB atlas of Florida vascular plants. Institute for Systematic Botany, University of South Florida, Tampa. 20 May 2009.
< http://www.florida.plantatlas.usf.edu >

Paper publications

Holm, L. G. et al. 1977. The world's worst weeds: Distribution and biology. The University Press of Hawaii, Honolulu.

Senseman, S. A. 2007. Herbicide Handbook, 9th ed., Weed Science Society of America, Lawrence, KS.

Wunderlin, R. P. 1998. Guide to the vascular plants of Florida. University Press of Florida, Gainesville.