Perhaps you should try some spelling variations:
"racial differential equations" » "radial differential equations", "fractal differential equations", "rail differential equations"
"racial difference 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: "((\"racial difference equations\") OR (\"racial differential equations\"))".
• Removing quotes may allow a broader search: (( racial difference equations ) OR ( racial differential equations )).
• Adding a wildcard symbol may retrieve word variants: (("racial difference equations") OR ("racial differential equations"))*.