Reference

Wilfried Stubbe, Peter H. Raven (1979/1980): A Genetic Contribution to the Taxonomy of Oenothera Sect. Oenothera (Including Subsections Euoenothera, Emersonia,Raimannia and Munzia) – Österreichische Botanische Zeitschrift = Plant Systematics and Evolution – 133: 39 - 59.