Perhaps you should try some spelling variations:
"greater decrease" » "greater decreased" (Expand Search), "greater increase" (Expand Search)
"per decrease" » "per decreased" (Expand Search), "per increase" (Expand Search)
"pierobon decrease" » "pierobon decreased" (Expand Search), "pierobon increase" (Expand Search)
"sperm decrease" » "sperm decreased" (Expand Search), "sperm increase" (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: "((\"greater decrease\") OR (((((\"per decrease\") OR (\"pierobon decrease\"))) OR (\"sperm decrease\"))))~".
• Removing quotes may allow a broader search: (( greater decrease ) OR ((((( per decrease ) OR ( pierobon decrease ))) OR ( sperm decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("greater decrease") OR ((((("per decrease") OR ("pierobon decrease"))) OR ("sperm decrease"))))*.