Perhaps you should try some spelling variations:
structural foundations » structural conditions, structural fluctuations, cultural foundations
structural equations » structural equation, structural evolution
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 foundations ) OR ( structural equations ))) OR ( structures functions )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(((( structural foundations ) OR ( structural equations ))) or ( structures functions ))".
• Adding a wildcard symbol may retrieve word variants: (((( structural foundations ) OR ( structural equations ))) or ( structures functions ))*.