Perhaps you should try some spelling variations:
level preprocessing » novel preprocessing (Expand search), series preprocessing (Expand search), the preprocessing (Expand search)
decreased level » decreased levels (Expand search), increased levels (Expand search)
that decreased » that decrease (Expand search), the decreased (Expand search), has decreased (Expand search)
decrease that » decrease the (Expand search), decrease at (Expand search), decrees that (Expand search)
decrease can » decrease in (Expand search), decrease and (Expand search), decrease at (Expand search)
can decrease » can increase (Expand search), and decrease (Expand search), the 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 that decreased level preprocessing ) OR ( decrease to decrease can decrease ))~".
• Adding a wildcard symbol may retrieve word variants: (( decrease that decreased level preprocessing ) OR ( decrease to decrease can decrease ))*.