diff --git a/Future-Modules.md b/Future-Modules.md
index dfdf638..0ae627f 100644
--- a/Future-Modules.md
+++ b/Future-Modules.md
@@ -107,7 +107,7 @@ Tons of these, too, and most people want at least two of these in a rack, if not
 ** cheap way to get to a slightly-detuned supersaw, with a voltage splitter or multiplexer module
 
 #### A VCO with hard sync
-?
+* See https://github.com/kassu/kassutronics/tree/master/documentation/VCO%203340 which is based on the 3340 but supports hard sync.  Is it possible to do hard sync without a purpose-built chip?  Is it worth it?
 
 ## Moar VCFs
 Everybody needs several VCFs with different behaviors.