Perhaps you should try some spelling variations:
"affect theory" » "effect theory", "effects theory", "effective theory"
"exact theory" » "effect theory", "exart theory", "exaction theory", "exagent theory"
"act theory" » "art theory", "action theory", "agent 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: (("affect theory") OR ((("act theory") OR ("exact theory")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"affect theory\") or (((\"act theory\") OR (\"exact theory\"))))".
• Removing quotes may allow a broader search: (( affect theory ) or ((( act theory ) OR ( exact theory )))).
• Adding a wildcard symbol may retrieve word variants: (("affect theory") or ((("act theory") OR ("exact theory"))))*.