SEARCH Articles Figures Tables Correlation energy with 40 Hylleraas function Equation, Hylleraas Explicitly correlated methods Hylleraas function Helium atom Hylleraas function Hylleraas Method Hylleraas Phys Hylleraas and James-Coolidge wave functions Hylleraas expansion Hylleraas function compared Hylleraas function methods Hylleraas functional Hylleraas functions Hylleraas integrals Hylleraas representation Hylleraas variational method Hylleraas variational principle Hylleraas wave function Hylleraas wavefunction Hylleraas wavefunctions Hylleraas-CI method Hylleraas-Undheim theorem Hylleraas-type basis functions The Hylleraas function The Hylleraas functional Total energy with 40 Hylleraas function Undheim-Hylleraas-Macdonald theorem Upper bounds and the Hylleraas-Undheim theorem