Perhaps you should try some spelling variations:
observational cohort » observational support, observational errors, observational method
observational cinema » observational clinical, observational context, observational economy
observation content » observation concept, observation consistent, observational context

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