Error arising from breakdown in the assumption that the liquid junction
potential remains constant when solution X is substituted for solution S in the operational cell.
PAC, 1985, 57, 531
(Definition of pH scales, standard reference values, measurement of pH and related terminology (Recommendations 1984))
on page 541
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook