3Williams P H,Cameron S A,Hines H M,et al.A simplified subgeneric classification of the bumblebees(genus Bombus)[J].Apidologie,2008,39(1):46-74.
4S. E. McGregor. Insect Pollination of Cultivated Crop Plants. Agricultural Research Service, P. 33 - 43, United States Department of Agriculture,lssued July 1976.