Perhaps you should try some spelling variations:
observational economy » observational astronomy, observational errors, observational coding
observational context » observational concepts, observational contacts, observation content
observational cohort » observational support, observational errors, observational methods
observational cinema » observational clinical, observational clues, observational case

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