1) J. W. Ross, "Calcium-Selective Electrode with Liquid Ion Exchanger", Science, 1967, 156, 1378.
2) J. Ruzicka, E. H. Hansen and J. Chr. Tjell, "Selectrode - The Universal Ion-selective Electrode Part VI. The Calcium(II) Selectrode Employing a New Ionexchanger in a Nonporous Membrane and a Solid-state Reference System", Anal. Chim. Acta, 1973, 67, 155.
3) H. M. Brown, J. P. Pemberton and J. D. Owen, "A Calcium-sensitive Microelectrode Suitable for Intracellular Measurement of Calcium(II) Activity", Anal. Chim. Acta, 1976, 85, 261.