diff --git a/README.md b/README.md
index 9488057..df43646 100644
--- a/README.md
+++ b/README.md
@@ -65,10 +65,25 @@ cd expressions
 ragel -Z scanner.rl && go test
 ```
 
+## References
+
+<https://shopify.github.io/liquid>
+
+<https://help.shopify.com/themes/liquid>
+
+<https://github.com/Shopify/liquid/wiki/Liquid-for-Designers>
+
+
 ## Attribution
 
+Kyoung-chan Lee's <https://github.com/leekchan/timeutil> for formatting dates.
+
 Michael Hamrah's [Lexing with Ragel and Parsing with Yacc using Go](https://medium.com/@mhamrah/lexing-with-ragel-and-parsing-with-yacc-using-go-81e50475f88f) was essential to understanding `go yacc`.
 
+The [original Liquid engine](https://shopify.github.io/liquid), of course, for the design and documentation of the Liquid template language.
+
+(That said, this is a clean-room implementation to make sure it just implements the documented design.)
+
 ## License
 
 MIT License