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