List A: species in Colorado that are designated by the Commissioner for eradication.
List B: weed species are species for which the Commissioner, in consultation with the state noxious weed advisory committee, local governments, and other interested parties, develops and implements state noxious weed management plans designed to stop the continued spread of these species.
Montana University Extension: http://store.msuextension.org/publications/AgandNaturalResources/MT201005AG.pdf
DiTomaso, J.M., G.B Kyser at al. 2013. Weed Control in Natural Areas in the Western United States. Weed Research and Information Center, University of California.
Colorado State University: http://extension.colostate.edu/topic-areas/agriculture/noxious-weeds-invasive-plant-species/
Colorado Department of Agriculture: https://www.colorado.gov/pacific/agconservation/canada-thistle
Whitson, T. (2006) Weeds of the west. Jackson, WY: Grande Teton Lithography
Merrill A. Ross : https://www.btny.purdue.edu/Pubs/WS/CanadaThistle/CanadaThistle.html