[5] Tang presented new combining rules for the calculation of van der Waals parameters in a study.
[7] In another paper, he discussed a simple theoretical model for the van der Waals potential at intermediate distances.
[9] His study about potentials for some rare gas and alkali-helium systems calculated using the surface integral method resulted in curves that correspond with the experimental and the ab initio theoretical data.
[10] Tang evaluated multipolar matrix elements using simple wave functions based on asymptomatic behavior and binding energies of the valence electron.
At low energies, it is considered as a remarkable approximation gained through truncating the series after the first two terms, which agrees with a semiclassical wavefunction formed after two manifolds of classical trajectories.