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