Perhaps you should try some spelling variations:
analytical measurement » analysis measurement, optical measurement, clinical measurement
optical measurements » physical measurements
valid analytical » based analytical, d analytical, valued analytic
valid optical » rapid optical, acid optical, solid optical

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: (( valid analytical measurement ) OR ( Valid optical measurements )).
• Adding a wildcard symbol may retrieve word variants: (( valid analytical measurement ) or ( Valid optical measurements ))*.