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