diff --git a/headers/os/drivers/usb/USB_audio.h b/headers/os/drivers/usb/USB_audio.h
index d3086e54da..3c492fe1c1 100644
--- a/headers/os/drivers/usb/USB_audio.h
+++ b/headers/os/drivers/usb/USB_audio.h
@@ -2,7 +2,7 @@
 #define USB_AUDIO_H
 
 // (Partial) USB Class Definitions for Audio Devices, version 1.0
-// (usb_audio_class_10.pdf)
+// Reference: http://www.usb.org/developers/devclass_docs/audio10.pdf
 
 #define USB_AUDIO_DEVICE_CLASS 			0x01
 #define USB_AUDIO_CLASS_VERSION			0x0100
diff --git a/headers/os/drivers/usb/USB_cdc.h b/headers/os/drivers/usb/USB_cdc.h
index 22e46ccf43..680de24dac 100644
--- a/headers/os/drivers/usb/USB_cdc.h
+++ b/headers/os/drivers/usb/USB_cdc.h
@@ -2,7 +2,7 @@
 #define USB_CDC_H
 
 // (Partial) USB Class Definitions for Communication Devices (CDC), version 1.1
-// (usbcdc11.pdf)
+// Reference: http://www.usb.org/developers/devclass_docs/usbcdc11.pdf
 
 #define USB_COMMUNICATION_DEVICE_CLASS 			0x02
 
diff --git a/headers/os/drivers/usb/USB_langIDs.h b/headers/os/drivers/usb/USB_langIDs.h
index e8e5d7c0f8..b33f71b347 100644
--- a/headers/os/drivers/usb/USB_langIDs.h
+++ b/headers/os/drivers/usb/USB_langIDs.h
@@ -2,7 +2,7 @@
 #define USB_LANGIDS_H
 
 // USB Language Identifiers, 3/29/2000, version 1.0
-// (http://www.usb.org/developers/data/USB_LANGIDs.pdf)
+// Reference: http://www.usb.org/developers/docs/USB_LANGIDs.pdf
 
 #define USB_LANGIDS_VERSION		0x0100	// version 1.0
 
diff --git a/headers/os/drivers/usb/USB_midi.h b/headers/os/drivers/usb/USB_midi.h
index 6c3f7e6456..5f2bbab4f1 100644
--- a/headers/os/drivers/usb/USB_midi.h
+++ b/headers/os/drivers/usb/USB_midi.h
@@ -4,7 +4,7 @@
 #include "USB_audio.h"
 
 // (Partial) USB Class Definitions for MIDI Devices, version 1.0
-// (usb_midi_class_10.pdf)
+// Reference: http://www.usb.org/developers/devclass_docs/midi10.pdf
 
 #define USB_MIDI_CLASS_VERSION		0x0100	// Class specification version 1.0