Performance Indicators for Wastewater Services. 1. Auflage, IWA-International Water Association. Inkl Software SIGMA Lite Wastewater (CD-ROM). www.iwapublishing.com ISBN 1-900222-90-6
Performance Indicators for Wastewater Services. 1. Auflage, IWA-International Water Association. Inkl Software SIGMA Lite Wastewater (CD-ROM). www.iwapublishing.com ISBN 1-900222-90-6. . 2004;56(3-4):a30-a30.
