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

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")).
• Removing quotes may allow a broader search: (( trubner technik leitfaden ) or ( grobner methods leitfaden )).
• Adding a wildcard symbol may retrieve word variants: (("trubner technik leitfaden") or ("grobner methods leitfaden"))*.