Perhaps you should try some spelling variations:
22stability theory » stability theory, bistability theory, disability theory
testability theory » stability theory, bistability theory, wettability theory
instability theory » stability theory, reliability theory, possibility 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: %((((22stability theory) OR (testability theory))) OR (((instability theory) OR (probability theory))))%22*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((((22stability theory) OR (testability theory))) or (((instability theory) or (probability theory))))%22*".