| Reference Label | Details |
|---|---|
| NIST Atomic Web | A. Kramida, Yu. Ralchenko, J. Reader, and NIST ASD Team, NIST Atomic Spectra Database (ver. 5.6.1), NIST Standard Reference Database #78, National Institute of Standards and Technology, Gaithersburg, MD 2018 Web: https://physics.nist.gov/asd (ex: http://physics.nist.gov/cgi-bin/AtData/main_asd) Note: latest version (as of Mar 2020) is ver. 5.7 |
| Morton 2006 | D. C. Morton, Q. Wu, and G. W. F. Drake, Can. J. Phys. 84, 83105 (2006) Energy Levels for the Stable Isotopes of Atomic Helium (4He I and 3He I) |