Czerednik, Anna, and Emil Nalborczyk. “Absorbtion of the Photosynthetically Active Radiation (PAR) in Canopy and Yield Formation by Leafy and Semi-Leafless Morphotypes of the Pea Plant (Pisum Sativum L.)”. Plant Breeding and Seed Science, vol. 44, Dec. 2000, pp. 85-93, http://ojs.ihar.edu.pl/index.php/pbss/article/view/820.