diff --git a/README.md b/README.md
index be47618..df5da01 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,9 @@ Graphics and infographics
 
 | Title       | Source          | Pdf |
 |:-------------|:------------------|:------|
-| Hutton's formula | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/hutton_formula.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/pdf/hutton_formula.pdf)  |
-| Strassnitzky's formula | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/strassnitzky_formula.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/pdf/strassnitzky_formula.pdf) |
-| Rolling circle squares itself | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/rolling_circle.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/pdf/rolling_circle.pdf) |
+| Hutton's formula | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/math/hutton_formula.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/math/pdf/hutton_formula.pdf)  |
+| Strassnitzky's formula | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/math/strassnitzky_formula.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/math/pdf/strassnitzky_formula.pdf) |
+| Rolling circle squares itself | [tex source](https://github.com/ulaulaman/tikzdraw/blob/master/math/rolling_circle.tex) | [pdf](https://github.com/ulaulaman/tikzdraw/blob/master/math/pdf/rolling_circle.pdf) |
 
 ## Astronomy