Perhaps you should try some spelling variations:
"racial differences equationss" » "racial differences equations", "racial difference equations", "racial differenced equations", "regional differences equationss"
"partial differential equation" » "partial difference equations"
"partial differential equations" » "partial difference equationss"

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