Safina, G. F., N. G. Tikhonova, V. G. Verzhuk, and N. A. Shubin. 2005. “Storage Influence of Apple and Cherry Pollen at Low and Ultralow Temperatures on Its Viability”. Problems of Cryobiology and Cryomedicine 15 (4):671-75. http://journal.cryo.org.ua/index.php/probl-cryobiol-cryomed/article/view/1217.