diff --git a/README.md b/README.md
index 9e1959d..4e345ac 100644
--- a/README.md
+++ b/README.md
@@ -1,14 +1,17 @@
 
 # Piecewise Readable Filter
 
-This is a pandoc filter manipulating [fenced_divs](https://pandoc.org/MANUAL.html#extension-fenced_divs) in pandoc markdown.
+This is a pandoc lua filter that manipulates [fenced_divs](https://pandoc.org/MANUAL.html#extension-fenced_divs) in pandoc markdown.
 
-Inspired by [this joke](https://www.zhihu.com/question/586807834/answer/2973535981).
+Inspired by [this joke](https://www.zhihu.com/question/586807834/answer/2973535981)(in chinese).
 
-useful refs:
+Example: `example/What is a group.pdf`
+
+Useful refs:
 - https://pandoc.org/lua-filters.html
+- https://hackage-content.haskell.org/package/pandoc-types-1.23.1/docs/Text-Pandoc-Definition.html
 
-# How does this work?
+## How does this work?
 
 `filter.lua` walks the AST. There are some special leaf nodes with a `include` attr which is a string containing labels of some other divs to be included here.
 
diff --git a/What is a group.pdf b/example/What is a group.pdf
similarity index 100%
rename from What is a group.pdf
rename to example/What is a group.pdf
diff --git a/algebraic_structures.md b/example/algebraic_structures.md
similarity index 100%
rename from algebraic_structures.md
rename to example/algebraic_structures.md
diff --git a/algebraic_structures.processed.md b/example/algebraic_structures.processed.md
similarity index 100%
rename from algebraic_structures.processed.md
rename to example/algebraic_structures.processed.md