Perhaps you should try some spelling variations:
interventional techniques » interaction techniques
observational context » observational concepts, observational contacts, observationsin contexts
observational cohort » observational support, observational errors, observational methods
observation content » observation concept, observation consistent, observation concepts

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: ((((observational context) OR (((interventional techniques) OR (observational cohort))))) OR (observation content)).
• Adding a wildcard symbol may retrieve word variants: ((((observational context) or (((interventional techniques) or (observational cohort))))) or (observation content))*.