Perhaps you should try some spelling variations:
decrease their » decrease the (Expand search), increase their (Expand search), decreases the (Expand search)
their mastery » the mastery (Expand search), their masses (Expand search), their markers (Expand search)
decrease akt » decrease at (Expand search), decrease and (Expand search), decrease after (Expand search)
akt decrease » and decrease (Expand search), not decrease (Expand search), any decrease (Expand search)
decrease may » decrease at (Expand search), decrease by (Expand search), decrease human (Expand search)
may decrease » may increase (Expand search), can decrease (Expand search), and decrease (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 akt decrease to decrease ) OR ( decrease may decrease their mastery ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease akt decrease to decrease ) OR ( decrease may decrease their mastery ))*.