Reference

Galina V. Degtjareva, Frank H. Hellwig, Dmitry D. Sokoloff, Siegfried Jost Casper (2003): Seed coat and embryo morphology in Pinguicula (Lentibulariaceae): implications for systematics and evolution – Palmarum Hortus Francofortensis - Wissenschaftliche Berichte – 7_2003: 25.