1. Adu S.V. , 1957 .‘Report on detailed soil survey of the Central Agricultural Station, Nyamkpala, Dagomba district’. Dept. Soil & Land Use Survey , Tech. Report 28 , 27
2. Aitchison G.D. , 1953 . ‘Soil morphology and foundation engineering’ . Proc. 3rd Intern. Conf. Soil Mech. Found. Eng. , Zurich , 1 : 3 – 7 .
3. Twenty-five years of application of soil survey principles in the practice of foundation engineering
4. Arman, A. and Thornton, S.I. 1972.‘Collapsible soils in Louisiana’, 131Baton Rouge: Louisiana State University. Division of Engineering Research, Bulletin 111