Perhaps you should try some spelling variations:
observational results » observational aspects, observational methods
observational clues » observational aspects, observational techniques, observational errors
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 (observational results))) OR (observation content)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((observational clues) OR (observational results))) or (observation content))".
• Adding a wildcard symbol may retrieve word variants: ((((observational clues) OR (observational results))) or (observation content))*.