El-Kabeir, S. M. M. M. M.; El-Hakiem, M. A. A.; Rashad, A. M. M. Natural Convection from a Permeable Sphere Embedded in a Variable Porosity Porous Medium Due to Thermal Dispersion. NAMC 2007, 12 (3), 345-357. https://doi.org/10.15388/NA.2007.12.3.14693.