diff --git a/src/references.gmo b/src/references.gmo
index 83f800e..7b88564 100644
--- a/src/references.gmo
+++ b/src/references.gmo
@@ -45,6 +45,8 @@ texts by solderpunk in the {gemini} protocol
 
 => https://wpmedia.wolfram.com/uploads/sites/13/2018/02/15-1-1.pdf Cook, Matthew (2004). "Universality in Elementary Cellular Automata" (PDF). Complex Systems. 15: 1–40.
 
+=> https://aphyr.com/posts/341-hexing-the-technical-interview Hexing the technical interview
+
 # non-electronic computers
 			
 => https://xkcd.com/505  - a bunch of rocks, randall munroe, xkcd