Perhaps you should try some spelling variations:
"20 means decrease" » "20 mean decrease" (Expand Search), "20 deaths decreased" (Expand Search), "_ means decrease" (Expand Search), "k means decrease" (Expand Search), "a means decrease" (Expand Search)
"5 ppm decrease" » "5 _ decrease" (Expand Search), "5 nn decrease" (Expand Search), "5 pa decreased" (Expand Search)
"50 we decrease" » "50 _ decrease" (Expand Search), "50 nn decrease" (Expand Search), "50 mean decrease" (Expand Search)
"50 a decrease" » "50 _ decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 _ decreases" (Expand Search), "50 μ decrease" (Expand Search), "50 c decrease" (Expand Search)

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("5 ppm decrease") OR ((((("50 a decrease") OR ("20 means decrease"))) OR ("50 we decrease"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"5 ppm decrease\") OR (((((\"50 a decrease\") OR (\"20 means decrease\"))) OR (\"50 we decrease\"))))".
• Removing quotes may allow a broader search: (( 5 ppm decrease ) OR ((((( 50 a decrease ) OR ( 20 means decrease ))) OR ( 50 we decrease )))).
• Adding a wildcard symbol may retrieve word variants: (("5 ppm decrease") OR ((((("50 a decrease") OR ("20 means decrease"))) OR ("50 we decrease"))))*.