Perhaps you should try some spelling variations:
"trubner methodischer leitfaden" » "uber methodische leitfaden", "erster methodischer leitfaden", "neuer methodischer leitfaden"
"trubner technik leitfaden" » "trubner methodik leitfaden", "uber technik leitfaden", "struktur technik leitfaden"
"trigger technik leitfaden" » "trigger methodik leitfaden", "trigger mechanism 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 ("trigger technik leitfaden"))) OR ("trubner methodischer leitfaden")).
• Removing quotes may allow a broader search: (((( trubner technik leitfaden ) or ( trigger technik leitfaden ))) or ( trubner methodischer leitfaden )).
• Adding a wildcard symbol may retrieve word variants: (((("trubner technik leitfaden") or ("trigger technik leitfaden"))) or ("trubner methodischer leitfaden"))*.