diff --git a/doc/paper/taler.tex b/doc/paper/taler.tex
index fb03fb36b..f954d1cc7 100644
--- a/doc/paper/taler.tex
+++ b/doc/paper/taler.tex
@@ -11,7 +11,8 @@
 \usetikzlibrary{positioning}
 \usetikzlibrary{calc}
 
-
+% Relate to:
+% http://fc14.ifca.ai/papers/fc14_submission_124.pdf
 
 % Terminology:
 % - SEPA-transfer -- avoid 'SEPA transaction' as we use