Ryan, M., Abeyratne, F., & Farrington, J. (1981). Animal draught: The economics of revival. Agrarian Research and Training Institute.
Chicago-viite (17. p.)Ryan, M., Fredrick Abeyratne, ja Joseph Farrington. Animal Draught: The Economics of Revival. Colombo, Sri Lanka: Agrarian Research and Training Institute, 1981.
MLA-viite (8. p.)Ryan, M., et al. Animal Draught: The Economics of Revival. Agrarian Research and Training Institute, 1981.
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