diff --git a/ausankey/ausankey.py b/ausankey/ausankey.py
index 885f022..197ad2c 100644
--- a/ausankey/ausankey.py
+++ b/ausankey/ausankey.py
@@ -603,8 +603,8 @@ def subplot(self, ii):
                 bot_lr = [lbot, rbot]
                 len_lr = [llen, rlen]
 
-                ys_d = create_curve(lbot, rbot)
-                ys_u = create_curve(lbot + llen, rbot + rlen)
+                ys_d = self.create_curve(lbot, rbot)
+                ys_u = self.create_curve(lbot + llen, rbot + rlen)
 
                 # Update bottom edges at each label
                 # so next strip starts at the right place
@@ -612,7 +612,7 @@ def subplot(self, ii):
                 node_pos_bot[1][lbl_r] += rlen
 
                 xx = np.linspace(x_lr[0], x_lr[1], len(ys_d))
-                cc = combine_colours(self.color_dict[lbl_l], self.color_dict[lbl_r], len(ys_d))
+                cc = self.combine_colours(self.color_dict[lbl_l], self.color_dict[lbl_r], len(ys_d))
 
                 for jj in range(len(ys_d) - 1):
                     self.ax.fill_between(
@@ -798,82 +798,66 @@ def sort_node_sizes(self, lbl, sorting):
         return sorted_labels
 
 
-###########################################
-
-
-def check_colors_match_labels(labels_lr, color_dict):
-    """Check that all labels in labels_lr are in color_dict"""
-
-    all_labels = pd.Series([*labels_lr[0], *labels_lr[1]]).unique()
-
-    missing = [label for label in all_labels if label not in color_dict]
-
-    if missing:
-        msg = "The color_dict parameter is missing " "values for the following labels: "
-        msg += "{}".format(", ".join(missing))
-        raise ValueError(msg)
-
-
-###########################################
-
-
-def create_curve(lpoint, rpoint):
-    """Create array of y values for each strip"""
-
-    num_div = 20
-    num_arr = 50
-
-    # half at left value, half at right, convolve
-
-    ys = np.array(num_arr * [lpoint] + num_arr * [rpoint])
-
-    ys = np.convolve(ys, 1 / num_div * np.ones(num_div), mode="valid")
-
-    return np.convolve(ys, 1 / num_div * np.ones(num_div), mode="valid")
-
-
-###########################################
-
-
-def combine_colours(c1, c2, num_col):
-    """Creates N colours needed to produce a gradient
-
-    Parameters
-    ----------
-
-    c1 : col
-        First (left) colour. Can be a colour string `"#rrbbgg"` or a colour list `[r, b, g, a]`
-
-    c1 : col
-        Second (right) colour. As above.
-
-    num_col : int
-        The number of colours N to create in the array.
-
-    Returns
-    -------
-
-    color_array : np.array
-        4xN array of numerical colours
-    """
-    color_array_len = 4
-    # if not [r,g,b,a] assume a hex string like "#rrggbb":
-
-    if len(c1) != color_array_len:
-        r1 = int(c1[1:3], 16) / 255
-        g1 = int(c1[3:5], 16) / 255
-        b1 = int(c1[5:7], 16) / 255
-        c1 = [r1, g1, b1, 1]
-
-    if len(c2) != color_array_len:
-        r2 = int(c2[1:3], 16) / 255
-        g2 = int(c2[3:5], 16) / 255
-        b2 = int(c2[5:7], 16) / 255
-        c2 = [r2, g2, b2, 1]
-
-    rr = np.linspace(c1[0], c2[0], num_col)
-    gg = np.linspace(c1[1], c2[1], num_col)
-    bb = np.linspace(c1[2], c2[2], num_col)
-    aa = np.linspace(c1[3], c2[3], num_col)
-
-    return np.array([rr, gg, bb, aa])
+    ###########################################
+    
+    
+    def create_curve(self, lpoint, rpoint):
+        """Create array of y values for each strip"""
+    
+        num_div = 20
+        num_arr = 50
+    
+        # half at left value, half at right, convolve
+    
+        ys = np.array(num_arr * [lpoint] + num_arr * [rpoint])
+    
+        ys = np.convolve(ys, 1 / num_div * np.ones(num_div), mode="valid")
+    
+        return np.convolve(ys, 1 / num_div * np.ones(num_div), mode="valid")
+    
+    
+    ###########################################
+    
+    
+    def combine_colours(self, c1, c2, num_col):
+        """Creates N colours needed to produce a gradient
+    
+        Parameters
+        ----------
+    
+        c1 : col
+            First (left) colour. Can be a colour string `"#rrbbgg"` or a colour list `[r, b, g, a]`
+    
+        c1 : col
+            Second (right) colour. As above.
+    
+        num_col : int
+            The number of colours N to create in the array.
+    
+        Returns
+        -------
+    
+        color_array : np.array
+            4xN array of numerical colours
+        """
+        color_array_len = 4
+        # if not [r,g,b,a] assume a hex string like "#rrggbb":
+    
+        if len(c1) != color_array_len:
+            r1 = int(c1[1:3], 16) / 255
+            g1 = int(c1[3:5], 16) / 255
+            b1 = int(c1[5:7], 16) / 255
+            c1 = [r1, g1, b1, 1]
+    
+        if len(c2) != color_array_len:
+            r2 = int(c2[1:3], 16) / 255
+            g2 = int(c2[3:5], 16) / 255
+            b2 = int(c2[5:7], 16) / 255
+            c2 = [r2, g2, b2, 1]
+    
+        rr = np.linspace(c1[0], c2[0], num_col)
+        gg = np.linspace(c1[1], c2[1], num_col)
+        bb = np.linspace(c1[2], c2[2], num_col)
+        aa = np.linspace(c1[3], c2[3], num_col)
+    
+        return np.array([rr, gg, bb, aa])
diff --git a/docs/reference.md b/docs/reference.md
index dfcb99d..72cb155 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -1,20 +1,8 @@
-# Reference
-
-## The `Sankey` class
-
-::: ausankey.Sankey
-
-## The `sankey` user function
+# The `sankey` user function
 
 ::: ausankey.sankey
 
-## Internal/private functions
+# The `Sankey` class
 
-### create_curve
-
-::: ausankey.create_curve
-
-### combine_colours
-
-::: ausankey.combine_colours
+::: ausankey.Sankey