Choy, C. L., & Yovanovich, M. (1989). Microcomputer Computation of Natural Convection Heat Transfer from Isothermal Spheres into Air for Rayleigh Numbers from 1.5 to 10^7 In Numerical Heat Transfer with Personal Computers and Supercomputing (Vol. 110, pp. 87-93). Philadelphia, PA: ASME National Heat Transfer Conference.