Perhaps you should try some spelling variations:
associated infection » associated infections
associated factor » associated factors, associate factor, associated pastors
associated vector » associated factors, associated secretory, associated operators

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: ((associated factor) OR (((associate director) OR (((associated vector) OR (associated infection)))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((associated factor) or (((associate director) or (((associated vector) OR (associated infection))))))".
• Adding a wildcard symbol may retrieve word variants: ((associated factor) or (((associate director) or (((associated vector) OR (associated infection))))))*.