1. Balls, A. K. Protein-digesting enzymes of papaya and pineapple. U.S.D.A. Circ. 631. 1941.
2. Macmillan, H. F. Tropical planting and gardening. 1935.
3. Papain production. Dept. Agi-., Peradeniya, Ceylon. Circ. 22.
4. The Pawpaw. Extract from the Queensland Agric. J. Queensland Dept. Agr. and Stock. 1954.
5. The Pawpaw. Tanganyika Dept. Agr. Pamph. No. 52. 1953.