A New and Flexible Architecture for the German Environmental Information Network. - Thomas Vögele; Martin Klenke; Fred A. Kruse; Stefan Groschupf (EnviroInfo, 2005)

InGrid 1.0 - The Nuts and Bolts of PortalU. - Martin Klenke; Fred A. Kruse; Hanno Lehmann; Thomas Riegel; Thomas Vögele (EnviroInfo, 2006)

Easy Access to Environmental Information with PortalU. - Thomas Vögele; Martin Klenke; Fred A. Kruse; Hanno Lehmann; Thomas Riegel (EnviroInfo, 2006)

Metadata Creation and Management of Distributed Data Catalogs with PortalU® and InGrid® 1.1. - Thomas Vögele; Martin Klenke; Fred A. Kruse (EnviroInfo (1), 2007)

PortalU® - a Tool to Support the Implementation of the European Environmental Information Directive. - Thomas Vögele; Martin Klenke; Fred A. Kruse; Hanno Lehmann; Christiane Giffei (EnviroInfo (2), 2007)

Shaping PortalU®/InGrid® to Meet the INSPIRE Requirements - First Experiences and Some Considerations on How to Efficiently Organize the German Spatial Data Infrastructure as INSPIRE Node. - Martin Klenke; Fred A. Kruse; Stefanie Uhrich; Christiane Giffei; Sybille Peters (EnviroInfo, 2008)

Einbindung von Kommunen in das Umweltportal Deutschland am Beispiel des Kommunalen PortalU® Niedersachsens. - Fred A. Kruse; Martin Klenke; Stefanie Uhrich; Christiane Giffei; Sybille Peters (EnviroInfo, 2008)

The Information Technology of the German Environmental Information Portal PortalU® as Tool for the European Level? - Stefanie Uhrich; Fred A. Kruse; Martin Klenke; Christiane Giffei; Sybille Peters (EnviroInfo, 2008)

Building a Soil Information Portal for Europe based on the PortalU Technology. - Katharina Feiden; Martin Klenke; Fred A. Kruse; Stefanie Konstantinidis (EnviroInfo (1), 2009)

Current state of the German Environmental Information Portal PortalU®. - Stefanie Konstantinidis; Fred A. Kruse; Martin Klenke (EnviroInfo (1), 2009)

PortalU®, a Tool for Building a Single Information Space in Europe (SISE) for the Environment. - Fred A. Kruse; Stefanie Konstantinidis; Martin Klenke (EnviroInfo (1), 2009)

OpenSearch - Simple formats to share environmental information. - Martin Klenke; Fred A. Kruse; Franz Schenk (EnviroInfo, 2010)

From Simple Data Sources to a Complex Information System: Integrating Heterogeneous Data Models into an Information Infrastructure for the Public Administration. - Franz Schenk; Fred A. Kruse; Martin Klenke (EnviroInfo, 2010)