Perhaps you should try some spelling variations:
"structural foundations" » "structural conditions", "structural fluctuations", "structural equations"
"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: (((("structures functions") OR ("structural foundations"))) OR ("structure functions")).
• Removing quotes may allow a broader search: (((( structures functions ) or ( structural foundations ))) or ( structure functions )).
• Adding a wildcard symbol may retrieve word variants: (((("structures functions") or ("structural foundations"))) or ("structure functions"))*.