diff --git a/docs/lib-arc.md b/docs/lib-arc.md
index 4f62e4b8..6e8a1623 100644
--- a/docs/lib-arc.md
+++ b/docs/lib-arc.md
@@ -7,6 +7,8 @@ Create an arc. You can pass a 2 element vector to define the central angle. Its
 - `radius` : The radius of the circle.
 - `angles` : A 2 element vector which defines the central angle. The first element of the vector is the beginning angle in degrees, and the second element is the ending angle.
 - `width_mode` : The default value is `"LINE_CROSS"`. The arc line will move outward by `width / 2` and inward by `width / 2`. If it's `"LINE_OUTWARD"`, the arc line moves outward by `width`. The `"LINE_INWARD"` moves the arc line inward by `width`.
+- `$fa`, `$fs`, `$fn` : Check [the circle module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle) for more details.
+
 
 ## Examples
     
diff --git a/docs/lib-circular_sector.md b/docs/lib-circular_sector.md
index 97544029..4d973965 100644
--- a/docs/lib-circular_sector.md
+++ b/docs/lib-circular_sector.md
@@ -6,7 +6,8 @@ Create a circular sector. You can pass a 2 element vector to define the central
 
 - `radius` : The radius of the circle.
 - `angles` : A 2 element vector which defines the central angle. The first element of the vector is the beginning angle in degrees, and the second element is the ending angle.
-
+- `$fa`, `$fs`, `$fn` : Check [the circle module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle) for more details.
+-
 ## Examples
 
     circular_sector(radius = 20, angles = [-50, -150]);  
diff --git a/docs/lib-hull_polyline3d.md b/docs/lib-hull_polyline3d.md
index 55da1104..eddad04f 100644
--- a/docs/lib-hull_polyline3d.md
+++ b/docs/lib-hull_polyline3d.md
@@ -6,9 +6,7 @@ Creates a 3D polyline from a list of `[x, y, z]` coordinates. As the name says,
 
 - `points` : The list of `[x, y, z]` points of the polyline. : A vector of 3 element vectors. The points are indexed from 0 to n-1.
 - `thickness` : The line thickness.
-- `$fa` : Fragment angle in degrees.
-- `$fs` : Fragment size in mm.
-- `$fn` : Resolution.
+- `$fa`, `$fs`, `$fn` : Check [the sphere module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Primitive_Solids#sphere) for more details,.
 
 ## Examples
 
diff --git a/docs/lib-line2d.md b/docs/lib-line2d.md
index c26dd031..d76a5ce7 100644
--- a/docs/lib-line2d.md
+++ b/docs/lib-line2d.md
@@ -1,7 +1,6 @@
 # line2d
 
-Creates a line from two points. When the end points are `CAP_ROUND`, 
-* you can use `$fa`, `$fs` or `$fn` to controll the circle module used internally.
+Creates a line from two points. When the end points are `CAP_ROUND`, you can use `$fa`, `$fs` or `$fn` to controll the `circle` module used internally.
 
 ## Parameters
 
@@ -10,6 +9,7 @@ Creates a line from two points. When the end points are `CAP_ROUND`,
 - `width` : The line width.
 - `p1Style` : The end-cap style of the point `p1`. The value must be `"CAP_BUTT"`, `"CAP_SQUARE"` or `"CAP_ROUND"`. The default value is `"CAP_SQUARE"`. 
 - `p2Style` : The end-cap style of the point `p2`. The value must be `"CAP_BUTT"`, `"CAP_SQUARE"` or `"CAP_ROUND"`. The default value is `"CAP_SQUARE"`. 
+- `$fa`, `$fs`, `$fn` : Check [the circle module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle) for more details.
 
 ## Examples
 
diff --git a/docs/lib-polyline2d.md b/docs/lib-polyline2d.md
index 3cc49914..88f8eade 100644
--- a/docs/lib-polyline2d.md
+++ b/docs/lib-polyline2d.md
@@ -9,6 +9,7 @@ Creates a polyline from a list of `x`, `y` coordinates. When the end points are
 - `width` : The line width.
 - `startingStyle` : The end-cap style of the starting point. The value must be `"CAP_BUTT"`, `"CAP_SQUARE"` or `"CAP_ROUND"`. The default value is `"CAP_SQUARE"`. 
 - endingStyle : The end-cap style of the ending point. The value must be `"CAP_BUTT"`, `"CAP_SQUARE"` or `"CAP_ROUND"`. The default value is `"CAP_SQUARE"`. 
+- `$fa`, `$fs`, `$fn` : Check [the circle module](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Using_the_2D_Subsystem#circle) for more details.
 
 ## Examples