Perhaps you should try some spelling variations:
"racial differences equations" » "racial difference equations", "racial differential equations", "racial differentes situations"
"regional differences equations" » "regional difference equations", "regional differential equations", "regional differentes situations", "regional conferences equations", "regional references equations", "fractional differences equations"
"regional difference equation" » "regional conference equation", "regional reference equation", "fractional difference equation", "regional difference equations", "regional differential equation", "regional 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 ((("regional differences equations") OR ("regional difference equation")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"racial differences equations\") or (((\"regional differences equations\") OR (\"regional difference equation\"))))".
• Removing quotes may allow a broader search: (( racial differences equations ) or ((( regional differences equations ) OR ( regional difference equation )))).
• Adding a wildcard symbol may retrieve word variants: (("racial differences equations") or ((("regional differences equations") OR ("regional difference equation"))))*.