*[http://files.sig3d.de/file/ag-qualitaet/20110531_Regeln_GML_final_EN.pdf Modeling Guide for 3D Objects - Part 1: Basics (Rules for Validating GML Geometries in CityGML)] ( Version 0.6.0, PDF, English Version ) | *[http://files.sig3d.de/file/ag-qualitaet/20110531_Regeln_GML_final_EN.pdf Modeling Guide for 3D Objects - Part 1: Basics (Rules for Validating GML Geometries in CityGML)] ( Version 0.6.0, PDF, English Version ) |