Gradient Correction to Local Exchange and Correlation Energy

in Orbital Theories of Molecules and Solids , Clarendon Press, Oxford, 1974, p. 95. 

Should it prove possible, in the future, to solve the Euler equation (146) to full chemical accuracy, the values of p for isolated atoms, and the single value of p for the molecule built up from these atoms, will be of great interest. It is clear from the way that p was introduced in the density theory [see especially equation (23)] that one could contemplate estimating it in an atomic ion from 

in Electrons in Finite and Infinite Structures , ed. P. Phariseau and L. Scheire, Plenum, New York, 1977, p. 236. 

Hedin and S. Lundqvist, in Solid State Physics , ed. F. Seitz, D. Turnbull, and H. Ehrenreich, Academic Press, New York, 1969, Vol. 23, p. 1. 

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