1. W.G. Jensen, The Lewis Acid-Base Concepts, Wiley-Interscience, New York, 1980.
2. G.C. Pimentel and A.L. McClellan, The Hydrogen Bond, W.H. Freeman, San Francisco, 1960.
3. K. Niedenzu, Adv. Chem. Ser., Vol. 42, 1964.
4. B. Swanson and D.F. Shriver, Inorg. Chem., 9(1970)1406.
5. E. Weber and F. Vogtle, in Topics in Current Chemistry, Vol. 98, Springer-Verlag, New York, 1981.