1. ASTM Method D 4251-89: Standard Test Method for Active Matter in Anionic Surfactants by Potentiometrie Titration. American Society for Testing and Materials, Philadelphia, USA.
2. Marron, T. U. and Schifferli, J. Ind. Eng. Chem., Anal. Edn, 18 (1946), 49.
3. ASTM Method D 4224-89: Standard Test Method for Anionic Determination by Para-toluidine Hydrochloride. American Society for Testing and Materials, Philadelphia, USA.
4. Cross, C. K. JAOCS, 67 (1990), 142–143.
5. ISO 2870: 1986: Surface active agents—Detergents—Determination of anion-active matter hydrolyzable and non-hydrolyzable under acid conditions. International Organization for Standardization, Geneva.