diff --git a/README.md b/README.md
index 133e737..479aa35 100644
--- a/README.md
+++ b/README.md
@@ -11,3 +11,4 @@ This seems intended by the creators of the language.
 then create a slice or slice of maps and append after each deeper level discovered...)
 - add docs
 - delph deeper into different Markdown implementations (like CommonMark)
+- add support for "Setext-style headers"
diff --git a/docs/john_gruber.md b/docs/john_gruber.md
new file mode 100644
index 0000000..e2011e0
--- /dev/null
+++ b/docs/john_gruber.md
@@ -0,0 +1,16 @@
+John Gruber is the creator of Markdown.\
+He describes the syntax here:\
+https://daringfireball.net/projects/markdown/syntax
+
+#### headers
+
+https://daringfireball.net/projects/markdown/syntax#header
+
+> Atx-style headers use 1-6 hash characters at the start \
+of the line, corresponding to header levels 1-6.
+
+=> that means header level 6 is the maximum level (vim and bat also do not highlight \
+level 7 headings)
+
+But there are also "Setext-style headers" that can only create \
+level 1 and 2 headers.