1997 IUCN red list of threatened plants (1997)

Annals of the Missouri Botanical Garden - Missouri Botanical Garden. (Missouri Botanical Garden Press, 2006)

Annals of the Missouri Botanical Garden - Missouri Botanical Garden. (Missouri Botanical Garden Press, 2006)

An environmental profile of the Black Sea Coast - Gillett, Harriet J. (WCMC, 1997)

List of rare, threatened and endemic plants in Europe (1982 edition) (1983)