Reference Label	Details
NIST Atomic Web	NIST Atomic Spectra Database, NIST Standard Reference Database #78, National Institute of Standards and Technology: Gaithersburg, MD 2002,
Erickson 1977	G. W. Erickson, J. Phys. Chem. Ref. Data 6, 831-869 (1977) Energy Levels of One-Electron Atoms
note std dev	Originally one std. dev. was given and was multiplied by 2 (for large or unknown number of measurements) or the appropriate Student-t factor (for a smaller number of determinations) to come closer to the desired 95% confidence limit.