Perhaps you should try some spelling variations:
"fractional differences equations" » "fractional difference equations", "functional differences equations", "fractionally differenced equations", "fractional difference equation", "fractional differential equations", "fractional differentes situations"
"national differences equations" » "national difference equation", "national differential equations", "national differentes situations", "functional differences equations", "regional differences equations", "generational differences equations", "rational differences equations", "fractional differences equations"
"national difference equations" » "national differential equations", "rational difference equations", "fractional difference equations", "functional difference 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: (((("national differences equations") OR ("fractional differences equations"))) OR ("national difference equations")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"national differences equations\") OR (\"fractional differences equations\"))) or (\"national difference equations\"))".
• Removing quotes may allow a broader search: (((( national differences equations ) OR ( fractional differences equations ))) or ( national difference equations )).
• Adding a wildcard symbol may retrieve word variants: (((("national differences equations") OR ("fractional differences equations"))) or ("national difference equations"))*.