Perhaps you should try some spelling variations:
"50 ngnn decrease" » "50 nn decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 ngnnn decrease" (Expand Search), "50 ngna decrease" (Expand Search), "50 ngn_ decreased" (Expand Search), "50 nsgnn decrease" (Expand Search), "50 nggnn decrease" (Expand Search), "50 μgnn decrease" (Expand Search)
"50 nga decrease" » "50 a decrease" (Expand Search), "50 nn decrease" (Expand Search), "50 mean decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 nsga decrease" (Expand Search), "50 ngga decrease" (Expand Search), "50 μga decrease" (Expand Search)
"50 n decrease" » "50 nn decrease" (Expand Search), "50 a decrease" (Expand Search), "50 _ decreased" (Expand Search), "50 ns decrease" (Expand Search), "50 ng decrease" (Expand Search), "50 μ decrease" (Expand Search)

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