Perhaps you should try some spelling variations:
general equations » integral equations
general relative » general relation, general relating, general relations
"general relativity" » "general relatively"

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: (("general relativity") OR ("((((general relative) or (general equations))ly) or (((general relative) or (general equations))))")).
• Removing quotes may allow a broader search: (( general relativity ) or ( ((((general relative) or (general equations))ly) or (((general relative) or (general equations)))) )).
• Adding a wildcard symbol may retrieve word variants: (("general relativity") or ("((((general relative) or (general equations))ly) or (((general relative) or (general equations))))"))*.