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2. Ault A (2008) Percy Julian, Robert Robinson and the identity of eserethole. J Chem Educ 85(11):1524–1530
3. Balfour JH (1861) Description of the plant which produces the ordeal bean of Calabar. Trans Roy Soc Edinburgh 22: 305–312 + plates XVI and XVII
4. Barger G (1936) From physostigmine to Prostigmin. Festschrift Emil C Barell, Basel, pp 7–17
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