I'm really struggling on even getting started on this problem. I have read the chapter several times now and I have tried to understand the explanations in the chapter. But I can't even get this problem started. All I ask is if anyone knows how to do this, can you just get me started or point me in the right direction so I can then take it from there? Thanks for any help. ___________ Prove the theorem <K|H|L> = (N!)1/2 <KHP|H|L> where |KHP> is the Hartree product corresponding to the determinant |K>, i.e. |K> = |Xm(X1)Xn(X2)...> and |KHP> = Xm(X1)Xn(X2)... Prove this theorem _______________ This problem is from "Modern Quantum Chemistry" by Szabo & Ostlund for anyone who is wondering.