Perhaps you should try some spelling variations:
"50 ppm decrease" » "50 ppm decreased" (Expand Search), "50 ppm increase" (Expand Search)
"_ ann decrease" » "_ ann decreased" (Expand Search), "_ ann increase" (Expand Search), "_ anna decrease" (Expand Search)
"50 _ decrease" » "50 _ decreased" (Expand Search), "50 _ increase" (Expand Search)
"50 ms decrease" » "50 ms decreased" (Expand Search), "50 ms 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: "((\"50 ppm decrease\") OR (((((\"_ ann decrease\") OR (\"50 _ decrease\"))) OR (\"50 ms decrease\"))))~".
• Removing quotes may allow a broader search: (( 50 ppm decrease ) OR ((((( _ ann decrease ) OR ( 50 _ decrease ))) OR ( 50 ms decrease ))))~.
• Adding a wildcard symbol may retrieve word variants: (("50 ppm decrease") OR ((((("_ ann decrease") OR ("50 _ decrease"))) OR ("50 ms decrease"))))*.