Perhaps you should try some spelling variations:
"generation theorem" » "separation theorem", "preparation theorem", "generation through"
"generation theory" » "generative theory", "iteration theory", "generation third"
"operators theory" » "operator 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: (("operators theory") OR ((("generation theory") OR ("generation theorem")))).
• Removing quotes may allow a broader search: (( operators theory ) or ((( generation theory ) or ( generation theorem )))).
• Adding a wildcard symbol may retrieve word variants: (("operators theory") or ((("generation theory") or ("generation theorem"))))*.