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 toc » decrease the (Expand search), decreased to (Expand search), decrease on (Expand search)
toc decrease » to decrease (Expand search), the decrease (Expand search), not decrease (Expand search)
decrease of » decrease in (Expand search)
of decrease » or decrease (Expand search), not decrease (Expand search), to 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 toc decrease of decrease ) OR ( decrease NOT decrease their mastery ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease toc decrease of decrease ) OR ( decrease NOT decrease their mastery ))*.