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