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diff --git a/doc/MQTT-SN_spec_v1.2.pdf b/doc/MQTT-SN_spec_v1.2.pdf
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+
+http://emqttd.io/docs/v2/
+
+or
+
+http://docs.emqtt.com/
+
+or
+
+http://emqttd-docs.rtfd.org
+
diff --git a/doc/mqtt-v3.1.1.pdf b/doc/mqtt-v3.1.1.pdf
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