Update "NOTICE.txt".
diff --git a/NOTICE.txt b/NOTICE.txt
index 6fe2e55..587cd7f 100644
--- a/NOTICE.txt
+++ b/NOTICE.txt
@@ -1,5 +1,5 @@
 Apache Commons Math
-Copyright 2001-2019 The Apache Software Foundation
+Copyright 2001-2020 The Apache Software Foundation
 
 This product includes software developed at
 The Apache Software Foundation (http://www.apache.org/).