diff --git a/DESCRIPTION b/DESCRIPTION
index 9355432..a2d1fb0 100755
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -8,7 +8,7 @@ Description: Computes probabilities related to group sequential designs for
     normally distributed test statistics. Enables to derive critical
     boundaries, power, drift, and confidence intervals of such designs.
     Supports the alpha spending approach by Lan-DeMets (1994)
-    <doi:10.1002/sim.4780131308>
+    <doi:10.1002/sim.4780131308>.
 Imports:
     tcltk,
     tcltk2,