diff --git a/README.md b/README.md
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@@ -20,6 +20,6 @@ Connect to the on-board ESP32 on the [RealDigital Blackboard](https://realdigita
 | Documentation                           | Not started |
 
 ## Useful Links
-* [ESP32 AT Instruction Set Documentation (pdf)](https://www.espressif.com/sites/default/files/documentation/esp32_at_instruction_set_and_examples_en.pdf)
+* [ESP32 AT Instruction Set Documentation](https://www.espressif.com/sites/default/files/documentation/esp32_at_instruction_set_and_examples_en.pdf) (pdf)
 * [RealDigital Blackboard Manual](https://www.realdigital.org/doc/9c908d94497abb1eac41175d1ab05b88) (web)
 * [RealDigital Blackboard Rev. B Manual](https://www.realdigital.org/downloads/1a63155aa0d45e6af2d1ca0ea5d1e53a.pdf) (pdf)