Perhaps you should try some spelling variations:
observational contacts » observational contrains, observational concepts, observational constrains
observational context » observational concepts, observation content, observationsin contexts
observational clues » observational aspects, observational results, observational techniques
observational case » observation case, observational basis, observational frame

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