Perhaps you should try some spelling variations:
"positive general theorems" » "position generale theorems", "positive minerals theorems", "primitive general theorems"
"positive general theory" » "position generale theory", "positive minerals theory", "primitive general theory"
"positive energy theorems" » "positive energy theory"

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: (("positive energy theorems") OR ((("positive general theorems") OR ("positive general theory")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"positive energy theorems\") or (((\"positive general theorems\") OR (\"positive general theory\"))))".
• Removing quotes may allow a broader search: (( positive energy theorems ) or ((( positive general theorems ) OR ( positive general theory )))).
• Adding a wildcard symbol may retrieve word variants: (("positive energy theorems") or ((("positive general theorems") OR ("positive general theory"))))*.