diff --git a/skimage/filter/rank/percentile_rank.pyx b/skimage/filter/rank/percentile_rank.pyx
index eee83a74..62cc4576 100644
--- a/skimage/filter/rank/percentile_rank.pyx
+++ b/skimage/filter/rank/percentile_rank.pyx
@@ -5,9 +5,12 @@ instead of using [min, max]. It means that isolated bright or dark pixels will
 not produce halos.
 
 The local histogram is computed using a sliding window similar to the method
-described in:
+described in [1].
 
-.. [1] Reference: Huang, T. ,Yang, G. ;  Tang, G.. "A fast two-dimensional
+References
+==========
+
+.. [1] Huang, T. ,Yang, G. ;  Tang, G.. "A fast two-dimensional
        median filtering algorithm", IEEE Transactions on Acoustics, Speech and
        Signal Processing, Feb 1979. Volume: 27 , Issue: 1, Page(s): 13 - 18.
 
diff --git a/skimage/filter/rank/tests/test_rank.py b/skimage/filter/rank/tests/test_rank.py
index 1c0481a5..43ff030f 100644
--- a/skimage/filter/rank/tests/test_rank.py
+++ b/skimage/filter/rank/tests/test_rank.py
@@ -322,7 +322,9 @@ def test_empty_selem():
 
 
 def test_otsu():
-    #
+    # test the local Otsu segmentation on a synthetic image
+    # (left to right ramp * sinus)
+
     test = np.tile(
         [128, 145, 103, 127, 165, 83, 127, 185, 63, 127, 205, 43,
             127, 225, 23, 127],