Perhaps you should try some spelling variations:
"leitfaden fur elektrotechnik" » "leitfaden zur elektrotechnik", "leitfaden fur elektrotechniker", "leitfaden u elektrotechnik"
"leitfaden der elektrotechnik" » "leitfaden zur elektrotechnik"

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: (("leitfaden fur elektrotechnik") OR ("leitfaden der elektrotechnik")).
• Removing quotes may allow a broader search: (( leitfaden fur elektrotechnik ) or ( leitfaden der elektrotechnik )).
• Adding a wildcard symbol may retrieve word variants: (("leitfaden fur elektrotechnik") or ("leitfaden der elektrotechnik"))*.