1. L.H. Baily (1935 ) The Standard Cyclopedia of Horticulture III , pp. 2648 -2649 . The Macmillan Comppany, New York.
2. British Pharmaceutical Codex (1949 ) pp. 512 -515 . The Pharmaceutical Press, London.
3. E. Claus (1970 ) In: Pharmacognosy , 6th edn. , p.207 . Edward Co.