Martin-Hou equation of state (1955) can be derived on the basis of the multi square-well nonspherical potential hard partical perturbation theory. With turther approximation van der Waals equation of state and Joffle equation of state modified by Barner and Adler can also be derived. Van der Waals equation is the simplest expansion of the perturbation theory. It is truncated to retain only the first-order perturbation term

the first power of the density expansion and the first term of the series expression of the hard particle reference fluid. Joffle-Barner-Adler equation retains higher-order perturbation terms

but unfortunately

it only has one term for the hard particle reierence fluid expression as in the case of van der Waals equation. Therefore the contributions of the repulsive forces can not be accurately represented. The theoretical basis of Martin-Hou equation is comparatively more adequate. It retains the higher-order perturbation terms and the higher-power terms of the hard particle reference fluid expression.