| | + | * Heywood, V.H.; Brummitt, R.K.; Culham, A. [et al.]. ''Flowering Plant Families of the World''. Ontario, Canada: Firefly Books, 2007, p. 280-282. ISBN 978-1-55407-206-4 |
| | + | * Stace, C. A.. ''New Flora of the British Isles''. Fourth. Middlewood Green, Suffolk, U.K.: C & M Floristics, 2019. ISBN 978-1-5272-2630-2 |