Give a URL for a paper about that protocol.

diff --git a/print-timed.c b/print-timed.c
index 395ab4bb7762947fe21664e5deb870018ff3c587..1b7d3ab85e3b5680793e0c337b6aed73d66e3b57 100644 (file)
--- a/print-timed.c
+++ b/print-timed.c
@@ -30,6 +30,8 @@
 
 /*
  * Time Synchronization Protocol
+ *
+ * http://docs.freebsd.org/44doc/smm/12.timed/paper.pdf
  */
 
 struct tsp_timeval {