Perhaps you should try some spelling variations:
sociological association » psychological association, ecological associations, psychological association's
biological association » biological associative, ecological association, ecological associations
urological association » ecological associations, archaeological association, psychological association

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: medical ((((biological association) OR (sociological association))) OR (urological association)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "medical ((((biological association) OR (sociological association))) or (urological association))".
• Adding a wildcard symbol may retrieve word variants: medical ((((biological association) OR (sociological association))) or (urological association))*.