Perhaps you should try some spelling variations:
"difference and function regulation" » "difference and protection regulation"
"difference and function equations" » "difference and functional equations", "difference and functional equation", "difference and function relations"
"difference and function relationships" » "difference and function relationship"

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: (("difference and function equations") OR ((("difference and function regulation") OR ("difference and function relationships")))).
• Removing quotes may allow a broader search: (( difference and function equations ) or ((( difference and function regulation ) or ( difference and function relationships )))).
• Adding a wildcard symbol may retrieve word variants: (("difference and function equations") or ((("difference and function regulation") or ("difference and function relationships"))))*.