Perhaps you should try some spelling variations:
"methode van bavel / gtt" » "methode vi bavel / gtt", "methode v bavel / gtt", "methode vii bavel / gtt"
"methode von bavel / gtt" » "methode von babel / gtt", "methode von gavel / gtt", "methode von baden / gtt"
"methode von havel / gtt" » "methode von gavel / gtt", "methode von hagel / gtt", "methode von hagen / gtt"

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("methode van bavel / gtt") OR ((("methode von bavel / gtt") OR ("methode von havel / gtt")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"methode van bavel / gtt\") or (((\"methode von bavel / gtt\") OR (\"methode von havel / gtt\"))))".
• Removing quotes may allow a broader search: (( methode van bavel / gtt ) or ((( methode von bavel / gtt ) OR ( methode von havel / gtt )))).
• Adding a wildcard symbol may retrieve word variants: (("methode van bavel / gtt") or ((("methode von bavel / gtt") OR ("methode von havel / gtt"))))*.