1. K. K. Unger, Porous Silica, Elsevier, New York 1979, p. 1.
2. H. Engelhardt, High Performance Liquid Chromatography, Springer-Verlag, New York 1979, p. 83.
3. R. C. Mackenzie, Differential Thermal Analysis, vol. 1, Academic Press, London 1970, p. 477.
4. L. R. Snyder and J. J. Kirkland, Introduction to Modern Liquid Chromatography, 2nd ed., John Wiley and Sons, Inc., New York 1979, p. 269.
5. Fernando Hernandez, private communication.