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