1. Keller, Mapes, and CheroffPhys. Rev. 108, 663 (1957).PHRVAO0031-899X
2. W. Low, Phys. Rev. 98, 426 (1955).PHRVAO0031-899X
3. S. P. Keller, J. Chem. Phys. 29, 180 (1958).JCPSA60021-9606
4. S. P. Keller and G. D. Pettit, J. Chem. Phys. (to be published).
5. K. Przibram, Z. Physik 107, 709 (1937); ZEPYAA0044-3328