1. Addens, TJ. J. 1939. The Distribution of Opium Cultivation and the Trade in Opium. Haarlem: Joh. Enschedé en Zonen. 129 p.
2. Aitchison, J. E. T. 1881. On the flora of the Kuram Valley, &. Afghanistan. J. Linn Soc. Bot.18: 1–113.
3. —. 1891. Notes to assist in a further knowledge of the products of Western Afghanistan and North-Eastern Persia. Trans. Proc. Bot. Soc. Edinburgh18: 1–228.
4. Akçasu, A. 1952. The changes experienced by the narcotics monopoly in Turkey. United Nations Dept. Social Affairs, Bull. Narcotics4(no.1): 6–9.
5. Annett, H. E. 1921. Investigations on Indian Opium, No. 2. The effect of environmental factors on the alkaloidal content and yield of latex from the opium poppy (Papaver somniferum) and the bearing of the work on the functions of alkaloids in plant life. Memoirs Dept. Agric. India (Chem. Ser.)6: 61–154.