Perhaps you should try some spelling variations:
"potential difference equationss" » "potential difference equation", "potential differences equations", "potential differenced equations"
"partial difference equations" » "racial differences 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: (("partial difference equations") OR ((((("partial differential equations") OR ("potential difference equationss"))) OR ("potential difference equationss")))).
• Removing quotes may allow a broader search: (( partial difference equations ) or ((((( partial differential equations ) or ( potential difference equationss ))) or ( potential difference equationss )))).
• Adding a wildcard symbol may retrieve word variants: (("partial difference equations") or ((((("partial differential equations") or ("potential difference equationss"))) or ("potential difference equationss"))))*.