CONTRIBUTORS

--- a/CONTRIBUTORS	Tue Dec 10 01:06:39 2019 +0100
+++ b/CONTRIBUTORS	Tue Dec 10 01:06:39 2019 +0100
@@ -6,6 +6,10 @@
 Contributions to this Isabelle version
 --------------------------------------
 
+* December 2019:
+  Basil Fürer, Andreas Lochbihler, Joshua Schneider, Dmitriy Traytel
+  Extension of lift_bnf to support quotient types.
+
 * October 2019: Maximilian Schäffeler
   Port of the HOL Light decision procedure for metric spaces.