Makino, Takashi T, and James D Thomson. “Innate or Learned Preference for Upward-Facing flowers?: Implications for the Costs of Pendent Flowers from Experiments on Captive Bumble Bees”. Journal of Pollination Ecology 9 (September 7, 2012): 79–84. Accessed April 26, 2024. https://pollinationecology.org/index.php/jpe/article/view/172.