1. R.S. Mulliken and B. Person, Molecular Complexes, Wiley, New York, p.3 (1969).
2. R.S. Mulliken and B. Person, Physical Chemistry, An Advanced Treatise, (H. Eyring, D. Henderson and W. Jost, Eds.) Vol. IIII, p. 537, Academic Press, New York, London (1969).
3. R.S. Mulliken, J. Chim. Phys., 61, 20 (1964).
4. O. Hassel and C. Rømming, Quart. Revs., 16, 1 (1962).
5. H. Pritzkow, Acta Cryst., B31, 1589 (1975) and Table 5 therein.