Perhaps you should try some spelling variations:
"racial differences equations" » "racial difference equation", "racial differentes situations", "racial differences variations"
"regional differences equations" » "regional difference equation", "regional differentes situations", "regional differences variations"
"racial differential equations" » "radial differential equations", "fractal differential equations", "rail differential equations"

Try widening your search to All Fields.

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