1. 1) Al-Mahbashi, A. M., & Elkady, T. Y. (2017): Prediction of unsaturated shear strength of expansive clays. Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 170(5), 407-420.
2. 2) Digioia, A. M., & Nuzzo, W. L. (1972): Fly ash as structural fill. Journal of the Power Division, 98(1), 77-92.
3. 3) Donald, I. B. (1957). Effective stresses in unsaturated non cohesive soils with controlled negative pore pressure. M. Eng. Sc. Thesis, University of Melbourne, Melbourne, Australia.
4. 4) Escario, V. and Juca, J. (1989): Strength and deformation of partly saturated soils. In Proceedings of the 12th International Conference on Soil Mechanics and Foundation Engineering, Rio de Janerio, 1989 (Vol. 3, pp. 43-46).
5. 5) Fisher, G. L., Prentice, B. A., Silberman, D., Ondov, J. M., Biermann, A. H., Ragaini, R. C., & McFarland, A. R. (1978): Physical and morphological studies of size-classified coal fly ash. Environmental Science & Technology, 12(4), 447-451.