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

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