Perhaps you should try some spelling variations:
associate directors » associated vectors, associated sectors, associated receptors
associated vector » associated factors, associated secretory, associated infection
associate factor » associated factors, associate editors, associated fatty

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: ((((associate director) OR (associate directors))) OR (((associate factor) OR (associated vector)))).
• Adding a wildcard symbol may retrieve word variants: ((((associate director) or (associate directors))) or (((associate factor) or (associated vector))))*.