USDA. National Agricultural Statistics Service.
In 2016 NASS began to collect data on honey bee health and pollination costs. Provides reliable, up-to-date statistics help track honey bee mortality.
USDA. APHIS. Wildlife Services.
HathiTrust Digital Library.
Thompson, D. Q. (1987). Spread, impact, and control of purple loosestrife (Lythrum salicaria) in North American wetlands. Washington, DC: U.S. Dept. of the Interior, Fish and Wildlife Service.
DOI. National Park Service.