Perhaps you should try some spelling variations:
"structural foundations" » "structural fluctuations", "structural equations", "cultural foundations"
"structural conditions" » "structural transitions", "structural considerations", "structural control"
"structural functional" » "structure function", "structure functions"

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