Perhaps you should try some spelling variations:
decrease their » decrease the (Expand search), increase their (Expand search), decreases the (Expand search)
risk decrease » risk decreases (Expand search), risk increase (Expand search), break decrease (Expand search)
decrease risk » decreased risk (Expand search), increase risk (Expand search), decrease in (Expand search)
their mastery » the mastery (Expand search), their masses (Expand search), their markers (Expand search)
decrease to » decreased to (Expand search), decrease toc (Expand search), decrease the (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 to decrease NOT decrease ) OR ( decrease risk decrease their mastery ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease to decrease NOT decrease ) OR ( decrease risk decrease their mastery ))*.