Perhaps you should try some spelling variations:
"structural functions" » "structural functional", "structural foundations", "structure function"
"structures functions" » "structure function", "structure functional", "structural functional"
"structure functions" » "structure function"

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: (("structural functions") OR ((("structures functions") OR ("structure functions")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"structural functions\") or (((\"structures functions\") OR (\"structure functions\"))))".
• Removing quotes may allow a broader search: (( structural functions ) or ((( structures functions ) OR ( structure functions )))).
• Adding a wildcard symbol may retrieve word variants: (("structural functions") or ((("structures functions") OR ("structure functions"))))*.