rnA simple method of calculation of the integrals of the Hylleraas-Ore wave function, used in the description of the four-particle system analogous to the H, molecule, is presented. The integrals corresponding to the kinetic energies of particles, to the Coulomb energy terms, and to the interparticle distances are given by the appropriate partial derivatives of a functional depending on the wave-function parameters. 0 1996 John Wiley & Sons,Inc.