1. J. W. DuMoxn and E. R. COHEN: In this volume and private communication.
2. Numerical values, found in older theoretical references (including ref. [10] of our bibliography), which are based on the atomic constants, should be treated with great caution: The older values of some atomic constants were in error by much more than the statistical errors in the older experiments (due to systematic errors not expected at the time).
3. We shall use throughout the symbol d for the LAPLACE operator (axz -}- ayz -~- ôz2), instead of the symbol V2 which is more commonly used in English and American texts.
4. x, and y are measured in atomic units.
5. Cf. Theory of the ZEEMAN effect, Sect. 45.