Perhaps you should try some spelling variations:
decrease their » decrease the (Expand search), increase their (Expand search), decreases the (Expand search)
their singing » choir singing (Expand search), the singing (Expand search), their silencing (Expand search)
decrease il » decreased il (Expand search), decrease hiv (Expand search), decrease of (Expand search)
il decrease » l decrease (Expand search), will decrease (Expand search), oil decreases (Expand search)
in decrease » in decreased (Expand search), on decrease (Expand search), pain decrease (Expand search)

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "(( decrease AND decrease il decrease ) OR ( decrease in decrease their singing ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease AND decrease il decrease ) OR ( decrease in decrease their singing ))*.