Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 pa decreased" (Expand Search), "5 ppm decrease" (Expand Search)
"50 nn decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 n decrease" (Expand Search), "59 nn decrease" (Expand Search)
"50 ns decrease" » "50 _ decrease" (Expand Search), "50 a decrease" (Expand Search), "50 we decrease" (Expand Search), "50 ms 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: "((\"50 ppm decrease\") OR (((\"50 nn decrease\") OR (\"50 ns decrease\"))))~".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((( 50 nn decrease ) OR ( 50 ns decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("50 ppm decrease") OR ((("50 nn decrease") OR ("50 ns decrease"))))*.