Remove citations in first line of docstring

skimage/filters/rank/generic.py

@@ -1,5 +1,5 @@
 """The local histogram is computed using a sliding window similar to the method
-described in [1].
+described in [1]_.
 
 Input image can be 8-bit or 16-bit, for 16-bit input images, the number of
 histogram bins is determined from the maximum value present in the image.
@@ -749,7 +749,7 @@ def tophat(image, selem, out=None, mask=None, shift_x=False, shift_y=False):
 
 def noise_filter(image, selem, out=None, mask=None, shift_x=False,
                  shift_y=False):
-    """Noise feature as described in [1].
+    """Noise feature.
 
     Parameters
     ----------
@@ -800,10 +800,11 @@ def noise_filter(image, selem, out=None, mask=None, shift_x=False,
 
 
 def entropy(image, selem, out=None, mask=None, shift_x=False, shift_y=False):
-    """Local entropy [1].
+    """Local entropy.
 
     The entropy is computed using base 2 logarithm i.e. the filter returns the
-    minimum number of bits needed to encode the local greylevel distribution.
+    minimum number of bits needed to encode the local greylevel
+    distribution.
 
     Parameters
     ----------