diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 76705bbd6..3c57f9155 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1198,6 +1198,17 @@ tools/generatejournal 3 5 5 --mixed >examples/mixed.journal
 
 ## Docs
 
+### Four kinds of documentation
+
+<div style="margin:1em 2em; font-style:italic;">
+"There is a secret that needs to be understood in order to write good
+software documentation: there isn’t one thing called documentation,
+there are four. They are: tutorials, how-to guides, explanation and
+technical reference. They represent four different purposes or
+functions, and require four different approaches to their creation."
+--[Daniele Procida] (https://news.ycombinator.com/item?id=21289832)
+</div>
+
 https://github.com/simonmichael/hledger/tree/master/doc
 
 Project documentation lives in a number of places: