1. Miranda, G.: Genera of Scrophulariaceae in the paramose of the venezuclan Andes. Brittonia 40(2), 235–239 (1988)
2. Willis, J.C.: A Dictionary of the Flowering Plants & Ferns, VII edn. University Press, Cambridge (1973)
3. Heywood V.: Las Planta Conores: Barcelona Reverte A (1985).
4. Mabberley, D.: The Plant Book, A Portable Dictionary of the Vascular Plants, 2nd edn. Cambridge University Press, Cambridge (1997)
5. Chaudhary, S.A.: The Flora of the Kingdom of Saudi Arabia. Ministry of Agriculture, Riyadh (2001)