diff --git a/readme.md b/readme.md
index 142c790..00759a4 100644
--- a/readme.md
+++ b/readme.md
@@ -23,10 +23,10 @@ They are easy to use and you do not need to be an expert to get first meaningful
   - [Support Tools](#support-tools)
   - [Misc Tools](#misc-tools)
 - [Hardware Tools](#hardware-tools)
-- [Bluetooth BLE Tools](#bluetooth-ble-tools)
-- [ZigBee Tools](#zigbee-tools)
-- [SDR Tools](#sdr-tools)
-- [RFID NFC Tools](#rfid-nfc-tools)
+  - [Bluetooth BLE Tools](#bluetooth-ble-tools)
+  - [ZigBee Tools](#zigbee-tools)
+  - [SDR Tools](#sdr-tools)
+  - [RFID NFC Tools](#rfid-nfc-tools)
 - [Books](#books)
 - [Research Papers](#research-papers)
 - [Case Studies](#case-studies)