Minor change to docstring

Author: SabineHaas

windpowerlib/wind_speed.py

@@ -114,8 +114,7 @@ def v_wind_hellman(v_wind, v_wind_height, hub_height, hellman_exp=None,
 
     Notes
     -----
-    The following equation is used [1]_,
-    [2]_, [3]_:
+    The following equation is used [1]_, [2]_, [3]_:
 
     .. math:: v_{wind,hub}=v_{wind,data}\cdot \left(\frac{h_{hub}}{h_{data}}
         \right)^\alpha