1. J. B. Howard, J. Chem. Phys. 5, 442 (1937). JCPSA60021-9606
2. More recently, H. C. Longuet‐Higgins, Mol. Phys. 6, 445 (1963), has considered the general problem of symmetry groups for molecules with large amplitude internal motions. In particular, he has discussed the internal and over‐all rotational, but not vibrational, symmetry of the ethane‐type molecule dimethylacetylene. Longuet‐Higgins’ results will be taken up in a future paper.MOPHAM0026-8976
3. (a) R. P. Bauman, J. Chem. Phys. 24, 13 (1956); JCPSA60021-9606
4. (b) R. Kopelman, Ph.D. thesis, Columbia University, 1960;
5. (c) C. V. Berney, L. R. Cousins, and F. A. Miller (to be published). We thank C. V. Berney and F. A. Miller for bringing this matter to our attention.