diff --git a/TASKS.txt b/TASKS.txt
index 2af9fc03..a17ecf35 100644
--- a/TASKS.txt
+++ b/TASKS.txt
@@ -25,6 +25,7 @@ Implement Algorithms
 - Graph cut segmentation
 - Fast 2D convex hull (consider using CellProfiler version)
   `Algorithm overview <http://www.tcs.fudan.edu.cn/rudolf/Courses/Algorithms/Alg_cs_07w/Webprojects/Zhaobo_hull/index.html#section26>`__.
+  `One free implementation <http://cm.bell-labs.com/cm/cs/who/clarkson/2dch.c>`_.
 - :strike:`Histograms of oriented gradients`
 - :strike:`Fast radon transform`
 - :strike:`Probabilistic Hough transform`