Terms conditions

Resolve #231

doc.zih.tu-dresden.de/docs/contrib/howto_contribute.md

@@ -11,9 +11,9 @@ contribute to this documentation as outlined below.
 ## Content Rules
 
 To ensure a high-quality and consistent documentation and to make it easier for readers to
-understand all content, we set some [content rules](content_rules.md). Please follow this rules when
-contributing! Furthermore, reviewing your changes take less time and your improvements appear faster
-on the official documentation.
+understand all content, we set some [content rules](content_rules.md). Please follow these rules
+when contributing! Furthermore, reviewing your changes take less time and your improvements appear
+faster on the official documentation.
 
 !!! note