Perhaps you should try some spelling variations:
decrease observed » decay observed (Expand search), case observed (Expand search)
observed objects » observed effects (Expand search), submerged objects (Expand search), buried objects (Expand search)
decrease the » decreases the (Expand search), decrease in (Expand search), decrease of (Expand search)
the decrease » to decrease (Expand search), and decrease (Expand search)
decrease hiv » decrease in (Expand search), decrease their (Expand search), decreased high (Expand search)
hiv decrease » via decrease (Expand search), hiv increase (Expand search), will decrease (Expand search)

You may be able to get more results by adjusting your search query.

• Removing quotes may allow a broader search: (( decrease the decrease hiv decrease ) OR ( decrease AND decrease observed objects ))~.