Perhaps you should try some spelling variations:
"operations theory" » "operators theory", "observations theory", "operator theory"
"generative theory" » "generalized theory", "integrative theory", "alternative theory"
"iteration theory" » "integration theory", "interaction theory", "vibration 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: (((("iteration theory") OR ("operations theory"))) OR ("generative theory")).
• Removing quotes may allow a broader search: (((( iteration theory ) or ( operations theory ))) or ( generative theory )).
• Adding a wildcard symbol may retrieve word variants: (((("iteration theory") or ("operations theory"))) or ("generative theory"))*.