Perhaps you should try some spelling variations:
"sound / according and reproducing / digital techniques" » "sound / according and reproductions / digital techniques", "sound / according and reproduction / digital techniques", "sound / according and reproducible / digital techniques"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"sound / according and reproducing / digital techniques\") OR (\"sound / according and producing / digital techniques\"))".
• Removing quotes may allow a broader search: (( sound / according and reproducing / digital techniques ) OR ( sound / according and producing / digital techniques )).
• Adding a wildcard symbol may retrieve word variants: (("sound / according and reproducing / digital techniques") OR ("sound / according and producing / digital techniques"))*.