Bertsch, A., Hrabé de Angelis, M., & Przemeck, G. K. H. 2010: A phylogenetic framework for the North American bumblebee species of the subgenus Bombus sensu stricto (Bombus affinis, B. franklini, B. moderatus, B. occidentalis & B. terricola) based on mitochondrial DNA markers. (Hymenoptera: Apidae: Bombus). - Beiträge Zur Entomologie = Contributions to Entomology 60(1): 229–242 - doi: 10.21248/contrib.entomol.60.1.229-242