EN/CityGML-Tutorial/chapter-1:-Intro-CityGML.md

@@ -21,7 +21,7 @@ The following example shows a CityModel (CityGML 2.0) that makes use of several
 
 ## CityGML Core
 
-The following UML diagram defines the CityGML top level class hierarchy (CityGML 2.0 standard document, fig. 23, p51).
+The following UML diagram defines the CityGML top level class hierarchy (based on CityGML 2.0 standard document, fig. 23, p51).
 
 ![CityGML_Core_UML.drawio](uploads/ecc982efbb15e857216fcb3e3b0b2ed5/CityGML_Core_UML.drawio.png)