Perhaps you should try some spelling variations:
"racial differences equation" » "racial differences equations", "racial differenced equations", "racial differences education", "facial differences equation", "social differences equation", "rational differences equation"
"regional differences equation" » "regional differences equations", "regional differenced equations", "regional differences education"
"racial difference equation" » "racial difference equations", "racial differential equation", "racial differential equations", "facial difference equation", "social difference equation", "rational difference equation"

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