Perhaps you should try some spelling variations:
"observational context" » "observational concepts", "observational contacts", "observation content"
"observational economy" » "observational astronomy", "observational cohort", "observational cinema"
"observational model" » "observation model", "observation models", "observations models"

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 model") OR ("observational context"))) OR ("observational economy")).
• Removing quotes may allow a broader search: (((( observational model ) or ( observational context ))) or ( observational economy )).
• Adding a wildcard symbol may retrieve word variants: (((("observational model") or ("observational context"))) or ("observational economy"))*.