WEDC Conference (6th : (1980 : Zaria), Pickford, J., & Ball, S. (1981). Water and waste engineering in Africa: 6th WEDCV conference 24 28 March 1980 at Ahmadu Bello University, Zaria, Nigeria. Department of Civil Engineering, University of Technology.
Παραπομπή σε μορφή Chicago (17η εκδ.)WEDC Conference (6th : (1980 : Zaria), John Pickford, και Susan Ball. Water and Waste Engineering in Africa: 6th WEDCV Conference 24 28 March 1980 at Ahmadu Bello University, Zaria, Nigeria. Loughborough: Department of Civil Engineering, University of Technology, 1981.
Παραπομπή σε μορφή MLA (9th εκδ.)WEDC Conference (6th : (1980 : Zaria), et al. Water and Waste Engineering in Africa: 6th WEDCV Conference 24 28 March 1980 at Ahmadu Bello University, Zaria, Nigeria. Department of Civil Engineering, University of Technology, 1981.