1. Flora d' Italia, Vol. 2, p. 194, Edagricole, Bologna, Italy (1982).
2. Tanaka's Cyclopedia of Edible Plants of the World, p. 223, Keigaku Publishing Co., Tokyo, Japan (1976).
3. Segreti e virtú delle piante medicinali, p. 153, Reader's Digest SpA, Milano, Italy (1981).