diff --git a/reading alexander.md b/reading alexander.md
index 53a3b6e6a..e753479d1 100644
--- a/reading alexander.md	
+++ b/reading alexander.md	
@@ -52,6 +52,7 @@
 		- feeling connected to the city life
 		- [[andreas]] it seems very opinionated, it depends on one's preferences. you might not care about the misfits and have fits with your lifestyle.
 		- [[simon]] four floors doesn't seem high density enough for city life. attitude towards skyrises changes a lot across cultures. singapore for example has a very different disposition towards them.
+			- most sustainable density is about six floors.
 - [[simon]]
 	- [[bus stop]]
 - [[alice]]