diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 6d4603f5b1..ed717ab549 100644
--- a/hw/sd/sdhci.c
+++ b/hw/sd/sdhci.c
@@ -1,6 +1,8 @@
 /*
  * SD Association Host Standard Specification v2.0 controller emulation
  *
+ * Datasheet: PartA2_SD_Host_Controller_Simplified_Specification_Ver2.00.pdf
+ *
  * Copyright (c) 2011 Samsung Electronics Co., Ltd.
  * Mitsyanko Igor <i.mitsyanko@samsung.com>
  * Peter A.G. Crosthwaite <peter.crosthwaite@petalogix.com>