diff --git a/README.md b/README.md
index 77ffae2..95b651a 100644
--- a/README.md
+++ b/README.md
@@ -4,3 +4,6 @@ http://www.hamskey.com/2024/04/introduction-to-uv-k5-hf-05-fullband.html#more
 https://github.com/phdlee/uvk5cec
 
 Starting with firmware version 0.5 HF.
+
+The base of the chirp driver is based on https://www.universirius.com/preppers/quansheng-uv-k5-manuale-del-firmware-ijv_2-9r5/#Firmware-IJV
+