Sphinx update (#479)

murrayrm · web-flow · commit 35f1e6486004 · 2020-12-28T11:01:17.000-08:00
* fix footnote reference in markov() docstring

* require sphinx 3.4 or higher for readthedocs
diff --git a/control/modelsimp.py b/control/modelsimp.py
@@ -407,7 +407,7 @@ def markov(Y, U, m=None, transpose=None):
         y[k] &= C x[k] + D u[k]
 
     given data for u and y.  The algorithm assumes that that C A^k B = 0 for
-    k > m-2 (see [1]).  Note that the problem is ill-posed if the length of
+    k > m-2 (see [1]_).  Note that the problem is ill-posed if the length of
     the input data is less than the desired number of Markov parameters (a
     warning message is generated in this case).
 
diff --git a/doc-requirements.txt b/doc-requirements.txt
@@ -1,3 +1,4 @@
+sphinx>=3.4
 numpy
 scipy
 matplotlib
