1. European Pharmacopoeia , Vol. II , Maisonneuve , S. A. France , 1971 , p. 53
2. 1st Supplement to the Pharmacopoeia of the USA , 18th Revision , 1971 , p. 37
3. The Pharmacopoeia of the USA , 18th Revision , 1970 , p. 832
4. British Pharmacopoeia 1973 , (a) p-241 , (b) pp. 98 and 437
5. International Pharmacopoeia ,, Supplement, Second Edition 1971 , p. 64