Perhaps you should try some spelling variations:
observational concepts » observation concepts, observational concerns, observational conceptual
observational context » observational contacts, observation content, observationsin contexts
observational cohort » observational support, observational methods, observational method
observational errors » observational methods, observational method, observational clues
observational cinema » observational clinical, observational economy, observational clues

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 errors))) OR (observational cinema))) OR (((observational context) OR (observational concepts)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((observational cohort) or (observational errors))) or (observational cinema))) or (((observational context) OR (observational concepts))))".
• Adding a wildcard symbol may retrieve word variants: ((((((observational cohort) or (observational errors))) or (observational cinema))) or (((observational context) OR (observational concepts))))*.