Łapiński, Mirosław, and Stefan Stojałowski. “Occurrence and Genetic Identity of Male Sterility-Inducing Cytoplasm in Rye (Secale spp.)”. Plant Breeding and Seed Science, vol. 48, Dec. 2003, pp. 7-23, http://ojs.ihar.edu.pl/index.php/pbss/article/view/714.