1. Ciambelli P, Corbo P, Liberti L and Lopez A 1988 Ammonium recovery from urban sewage by natural zeolites. In Occurence, Properties and Utilization of Natural Zeolites. Eds. D Kalló and H S Sherry, pp 501–510. Akadémiai Kiadó, Budapest, Hungary.
2. Collela C and Aiello R 1988 Ammonium removal from tannery sewages by selective ion exchange using natural phillipsite. In Occurence, Properties and Utilization of Natural Zeolites. Eds. D Kalló and H S Sherry. pp 491–500. Akadémiai Kiadü, Budapest, Hungary.
3. Hagiwara Z and Uchida M 1978 Ion-exchange reactions of processed zeolite and its application to the removal of ammonia-nitrogen in wastes. In Natural Zeolites: Occurence, Properties, Use. Eds. L B Sand and F A Mumpton. pp 463–470. Pergamon Press, New York, USA.
4. KolouSek D, Procházková E, Seidl V and Šmejkalová M 1990 Zpu-sob pŕipravy zeolitu. Czech Patent Application No 04530-90R, C-01-B-33/34.
5. Kovanda F, Koloušek D, Seidl V, Procházková E and Obšasniková J 1994 Utilization of synthetic phillipsite as a means for decreasing the concentration of ammonium ions in waste water. Ceramics-Silikáty 38, 75–79.