Add Arnaud for his efforts on multi-arg set operations.
diff --git a/Misc/ACKS b/Misc/ACKS
index e705a4b..43c9a0e 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -156,6 +156,7 @@
 Jonathan Dasteel
 John DeGood
 Vincent Delft
+Arnaud Delobelle
 Erik Demaine
 Roger Dev
 Raghuram Devarakonda