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

Try widening your search to All Fields.

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