Perhaps you should try some spelling variations:
observational concepts » observation concepts, observational concerns, observational conceptual
observational clues » observational aspects, observational results, observational techniques
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 clues) OR (((observation content) OR (observational concepts)))).
• Adding a wildcard symbol may retrieve word variants: ((observational clues) or (((observation content) or (observational concepts))))*.