diff --git a/DESCRIPTION b/DESCRIPTION
index 57fbad9..22ba0ce 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,