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