diff --git a/app/graph-tool.md b/app/graph-tool.md
index 080b88aa..eb06d010 100644
--- a/app/graph-tool.md
+++ b/app/graph-tool.md
@@ -12,7 +12,7 @@ draft: false
 
 ## Graphics language 
 - [Asymptote](https://asymptote.sourceforge.io/)
-- [PyX](https://en.wikipedia.org/wiki/PyX_(vector_graphics_language))
+- [PyX](https://en.wikipedia.org/wiki/PyX_\(vector_graphics_language\))
 - [Tikz](https://github.com/pgf-tikz/pgf)
 - [PSTricks](https://en.wikipedia.org/wiki/PSTricks)
 
@@ -33,4 +33,4 @@ draft: false
 ## Graphics and Plotter
 - [touchplot.com - Online plotter and graphing tool - Create graphs and charts online.](https://touchplot.com/#)
 - [Online Graph Maker · Plotly Chart Studio](https://chart-studio.plotly.com/create/#/)
-- [Online Graph Maker - Plotvar](http://www.plotvar.com/index.php)
\ No newline at end of file
+- [Online Graph Maker - Plotvar](http://www.plotvar.com/index.php)