Perhaps you should try some spelling variations:
technik leitfaden » methodik leitfaden
methods leitfaden » methode leitfaden, methodik leitfaden, methodischer leitfaden
trubner technik » uber technik, trigger technik, struktur technik
grobner methods » greener methods, proper methods, frontier methods

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: (( trubner technik leitfaden ) OR ( grobner methods leitfaden )).
• Adding a wildcard symbol may retrieve word variants: (( trubner technik leitfaden ) or ( grobner methods leitfaden ))*.