H.K. Winkler, W. Widmann: The Sulaibiya Wastewater Treatment and Reclamation Project, Proceedings of 10^th IWA Specialised Conference Design, Operation and Economics of Large Wastewater Treatment Plants, September 2007, Vienna , Austria

W. Widmann, H.K. Winkler, G. Vaccaro: Das Sulaibiya Wastewater Treatment and Reclamation Project, Begleitbuch zur 6. Aachener Tagung Siedlungswasserwirtschaft und Verfahrenstechnik, Membrantechnik in der Wasseraufbereitung und Abwasserbehandlung, -Perspektiven, Neuentwicklungen und Betriebserfahrungen im In- und Ausland, Oktober 2005, Aachen, Deutschland

W. Widmann, H.K. Winkler, W. van Appeldorn: Expansion and Upgrading of Innsbruck Wastewater Treatment Plant, Proceedings of the Water Environment Federation Technical Conference and Exhibition (WEFTEC ASIA), Municipal Wastewater Treatment, Wastewater Treatment Research, Industrial/Hazardous Waste Technologies, March 1998, Singapore , Indonesia

H.K. Winkler, W. Widmann: Comparison of Single Stage and Two Stage Activated Sludge Processes for the Expansion of Innsbruck Wastewater Treatment Plant, Water Science and Technology, Volume 12, Pages 69-79, 1994

H.K. Winkler, W. Widmann: Comparison of Single Stage and Two Stage Activated Sludge Processes for the Expansion of Innsbruck Wastewater Treatment Plant, Proceedings of 2^nd IAWQ International Specialised Conference on Upgrading of Wastewater Treatment Plants, September 1993, Berlin, Germany