diff --git a/back_running/README.md b/back_running/README.md
index 1d150df..908751f 100644
--- a/back_running/README.md
+++ b/back_running/README.md
@@ -33,4 +33,5 @@
 
 * [dune for Portion of Daily Gas Used by Backrunning Bot Contracts](https://dune.com/phabc/backrunning-bots-gas-consumption)
 * [backrunning study for bZx IDO](https://amanusk.medium.com/the-fastest-draw-on-the-blockchain-bzrx-example-6bd19fabdbe1)
+* [ef discussion on random ordering of equally-priced txs](https://github.com/ethereum/go-ethereum/issues/21350)