I would like to present to a wide circle of the readers working in quantum chem- istry and solid-state physics, as ,,*ell as in other fields of many-body physics and its interfaces, this book deyoted to density functional theory written by my colleagues Eugene S. Kryachko and Eduardo Y. Ludena. Their ways to this theory are rather different although basically both of them are quantum chemical. Eugene S. Kryachko came to energy density functional theory from the theory of reduced density matrices, and Eduardo '. Ludena dewloped earlier the concept of loges in quantum chemistry. Neyertheless,...