Perhaps you should try some spelling variations:
"racial differences equations" » "racial difference equation", "racial differential equations", "racial differentes situations", "regional differences equations", "national differences equations"
"racial different situations" » "racial different nations", "racial difficult situations", "racial difference situations", "facial difference situations", "spatial different situations"
"potential difference equations" » "potential differential equations"

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: (((("racial differences equations") OR ("racial different situations"))) OR ("potential difference equations")).
• Removing quotes may allow a broader search: (((( racial differences equations ) or ( racial different situations ))) or ( potential difference equations )).
• Adding a wildcard symbol may retrieve word variants: (((("racial differences equations") or ("racial different situations"))) or ("potential difference equations"))*.