Ollerton, J., J. R. Rouquette, and T. D. Breeze. “Insect Pollinators Boost the Market Price of Culturally Important Crops: Holly, Mistletoe and the Spirit of Christmas”. Journal of Pollination Ecology, vol. 19, Dec. 2016, pp. 93-97, doi:10.26786/1920-7603(201)6.