diff --git a/README.md b/README.md
index 4e9fd448..94173782 100644
--- a/README.md
+++ b/README.md
@@ -356,7 +356,7 @@ These examples incubate dotSCAD and dotSCAD refactors these examples. See [examp
  Signature | Description
 --|--
 [**surface/sf_curve**(levels, curve_path, ...)](https://openhome.cc/eGossip/OpenSCAD/lib3x-sf_curve.html) | curve a photo.
-**surface/sf_splines**(ctrl_pts, row_spline, column_spline) | generalized-spline surface.
+[**surface/sf_splines**(ctrl_pts, row_spline, column_spline)](https://openhome.cc/eGossip/OpenSCAD/lib3x-sf_splines.html) | generalized-spline surface.
 
 ## Triangle
 
diff --git a/docs/images/lib3x-sf_splines-1.JPG b/docs/images/lib3x-sf_splines-1.JPG
new file mode 100644
index 00000000..87b6f53c
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diff --git a/docs/lib3x-sf_splines.md b/docs/lib3x-sf_splines.md
new file mode 100644
index 00000000..74e69ee7
--- /dev/null
+++ b/docs/lib3x-sf_splines.md
@@ -0,0 +1,62 @@
+# sf_splines
+
+Given a set of control points and spline functions, the `sf_splines` function returns surface points.
+
+**Since:** 3.1
+
+## Parameters
+
+- `ctrl_pts` : A set of control points. See examples below.
+- `row_spline` : The spline function for row points.
+- `column_spline` : The spline function for columns points. Default to `row_spline`.
+
+## Examples
+
+If you want to make a bezier surface:
+
+	use <bezier_curve.scad>;
+	use <function_grapher.scad>;
+	use <surface/sf_splines.scad>;
+
+	ctrl_pts = [
+		[[0, 0, 20],  [60, 0, -35],   [90, 0, 60],    [200, 0, 5]],
+		[[0, 50, 30], [100, 60, -25], [120, 50, 120], [200, 50, 5]],
+		[[0, 100, 0], [60, 120, 35],  [90, 100, 60],  [200, 100, 45]],
+		[[0, 150, 0], [60, 150, -35], [90, 180, 60],  [200, 150, 45]]
+	];
+
+	thickness = 2;
+	t_step = 0.05;
+
+	bezier = function(points) bezier_curve(t_step, points);
+
+	function_grapher(sf_splines(ctrl_pts, bezier), thickness);
+
+![sf_splines](images/lib3x-sf_splines-1.JPG)
+
+The following figure shows controll points and bazier curves around the surface.
+
+![sf_splines](images/lib3x-sf_splines-2.JPG)
+
+If you want to make a bspline surface:
+
+	use <bspline_curve.scad>;
+	use <function_grapher.scad>;
+	use <surface/sf_splines.scad>;
+
+	ctrl_pts = [
+		[[0, 0, 20],  [60, 0, -35],   [90, 0, 60],    [200, 0, 5]],
+		[[0, 50, 30], [100, 60, -25], [120, 50, 120], [200, 50, 5]],
+		[[0, 100, 0], [60, 120, 35],  [90, 100, 60],  [200, 100, 45]],
+		[[0, 150, 0], [60, 150, -35], [90, 180, 60],  [200, 150, 45]]
+	];
+
+	thickness = 2;
+	t_step = 0.05;
+	degrees = 2;
+
+	bspline = function(points) bspline_curve(t_step, degrees, points);
+
+	function_grapher(sf_splines(ctrl_pts, bspline), thickness);
+
+![sf_splines](images/lib3x-sf_splines-3.JPG)
\ No newline at end of file
diff --git a/src/surface/sf_splines.scad b/src/surface/sf_splines.scad
index e3b5e95d..4a4108f7 100644
--- a/src/surface/sf_splines.scad
+++ b/src/surface/sf_splines.scad
@@ -1,3 +1,13 @@
+/**
+* sf_splines.scad
+*
+* @copyright Justin Lin, 2021
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib3x-sf_splines.html
+*
+**/ 
+
 function sf_splines(ctrl_pts, row_spline, column_spline) =
     let(
         leng_ctrl_pts = len(ctrl_pts),
@@ -12,79 +22,4 @@ function sf_splines(ctrl_pts, row_spline, column_spline) =
     [
 	    for(c = 0; c < leng_r_pts0; c = c + 1)
             cspline([for(r = 0; r < leng_r_pts; r = r + 1) r_pts[r][c]]) 
-    ];
-
-/*
-use <bspline_curve.scad>;
-use <function_grapher.scad>;
-use <surface/sf_splines.scad>;
-
-ctrl_pts = [
-    [[0, 0, 20],  [60, 0, -35],   [90, 0, 60],    [200, 0, 5]],
-    [[0, 50, 30], [100, 60, -25], [120, 50, 120], [200, 50, 5]],
-    [[0, 100, 0], [60, 120, 35],  [90, 100, 60],  [200, 100, 45]],
-    [[0, 150, 0], [60, 150, -35], [90, 180, 60],  [200, 150, 45]]
-];
-
-thickness = 2;
-t_step = 0.05;
-degrees = 2;
-
-row_spline = function(points) bspline_curve(t_step, degrees, points);
-column_spline = function(points) bspline_curve(t_step, degrees, points);
-
-function_grapher(sf_splines(ctrl_pts, row_spline, column_spline), thickness);
-*/
-
-/*
-
-use <bezier_curve.scad>;
-use <function_grapher.scad>;
-use <surface/sf_splines.scad>;
-
-ctrl_pts = [
-    [[0, 0, 20],  [60, 0, -35],   [90, 0, 60],    [200, 0, 5]],
-    [[0, 50, 30], [100, 60, -25], [120, 50, 120], [200, 50, 5]],
-    [[0, 100, 0], [60, 120, 35],  [90, 100, 60],  [200, 100, 45]],
-    [[0, 150, 0], [60, 150, -35], [90, 180, 60],  [200, 150, 45]]
-];
-
-thickness = 2;
-t_step = 0.05;
-
-row_spline = function(points) bezier_curve(t_step, points);
-column_spline = function(points) bezier_curve(t_step, points);
-
-function_grapher(sf_splines(ctrl_pts, row_spline, column_spline), thickness);
-
-*/
-
-/*
-
-use <curve.scad>;
-use <function_grapher.scad>;
-use <surface/sf_splines.scad>;
-
-use <hull_polyline3d.scad>;
-
-ctrl_pts = [
-    [[0, 0, 20],  [20, 0, -15], [90, 0, 30], [200, 0, 5]],
-    [[0, 20, 30], [30, 30, -25], [80, 40, 20], [100, 50, 5]],
-    [[0, 100, 0], [20, 90, 15],  [90, 100, 10],  [100, 100, 45]],
-    [[0, 110, 0], [40, 120, -35], [90, 130, 20],  [120, 120, 15]]
-];
-
-thickness = 2;
-t_step = 0.05;
-
-row_spline = function(points) curve(t_step, points);
-column_spline = function(points) curve(t_step, points);
-
-function_grapher(sf_splines(ctrl_pts, row_spline, column_spline), thickness);
-
-for(i = [0:3]) {
-    %hull_polyline3d(ctrl_pts[i]);
-    #hull_polyline3d(curve(t_step, ctrl_pts[i]));
-}
-
-*/
\ No newline at end of file
+    ];
\ No newline at end of file