1. R. Sweet, Hortus Britannicus, 2nd Ed, p. 247. J. Ridgway, London, (1830).
2. F. Conti, G. Abbate, A. Alessandrini and C. Blasi, An Annotated Checklist of the Italian Vascular Flora, p. 170. Palombi Press, Rome, Italy (2005).
3. R. Schicchi and A. Geraci, Verdure spontanee di Sicilia, pp. 157–159. Ed. IDIMED, Palermo (2015).