Some of the problems outlined above become somewhat less severe if, instead of insisting on a complete projection of the spherical harmonic components of the wave functions around each ion, one performs only a partial projection as in the Kleinman-Bylander scheme. However, the scheme outlined below can be applied to any number of projections and hence allows the spherical harmonic components of the wave functions to be projected to any degree of accuracy (as in the enhanced projection schemes mentioned above).