US National Institute of Standards and Technology official density-functional theory results for the electronic structure of atoms [To validate your own calculations!]
On-line version of "What Every Computer Scientist Should Know About Floating-Point Arithmetic".
Numerical Recipes Book and Code Online (free of charge when accessed from a Cornell IP address on the Cornell network)
Books and original articles on density-functional theory:
- Books:
  - Density-Functional Theory of Atoms and Molecules (International Series of Monographs on Chemistry, No 16) by Robert G. Parr, Weitao Yang.
  - A Chemist's Guide to Density Functional Theory, 2nd Edition, by Wolfram Koch, Max C. Holthausen.
- Original articles:
  - "Inhomogeneous Electron Gas," by P. Hohenberg and W. Kohn, Physical Review 136, B864-B871 (1964).
  - "Self-Consistent Equations Including Exchange and Correlation Effects," by W. Kohn and L. J. Sham, Physical Review 140, A1133-A1138 (1965).
  - "Correlation Energy of an Electron Gas at High Density," by M. Gell-Mann and K.A. Brueckner, Physical Review 106, 364-368 (1957).
  - "New algebraic formulation of density functional calculation,'' by Sohrab Ismail-Beigi and T.A. Arias, Computer Physics Communications 128:1-2, 1-45 (June 2000).