Perhaps you should try some spelling variations:
"social differences situations" » "social differentes situations", "social different situations", "social difference simulations", "racial differences situations", "social preferences situations", "regional differences situations"
"racial difference equations" » "racial differential equations", "racial differences equations", "facial difference equations", "social difference equations"

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"social differences situations\") OR (\"racial difference equations\"))".
• Removing quotes may allow a broader search: (( social differences situations ) OR ( racial difference equations )).
• Adding a wildcard symbol may retrieve word variants: (("social differences situations") OR ("racial difference equations"))*.