diff --git a/docs/en/modules/u8g.md b/docs/en/modules/u8g.md
index c6cdb01e..944bb1d3 100644
--- a/docs/en/modules/u8g.md
+++ b/docs/en/modules/u8g.md
@@ -35,7 +35,7 @@ scl = 6
 i2c.setup(0, sda, scl, i2c.SLOW)
 ```
 ### SPI connection
-The HSPI module is used, so certain pins are fixed:
+The HSPI module is used ([more information](http://d.av.id.au/blog/esp8266-hardware-spi-hspi-general-info-and-pinout/)), so certain pins are fixed:
 
 - HSPI CLK = GPIO14
 - HSPI MOSI = GPIO13
diff --git a/docs/en/modules/ucg.md b/docs/en/modules/ucg.md
index bf3b2fe4..c3aa9166 100644
--- a/docs/en/modules/ucg.md
+++ b/docs/en/modules/ucg.md
@@ -15,7 +15,7 @@ This integration is based on [v1.3.3](https://github.com/olikraus/Ucglib_Arduino
 
 ### SPI Connection
 
-The HSPI module is used, so certain pins are fixed:
+The HSPI module is used ([more information](http://d.av.id.au/blog/esp8266-hardware-spi-hspi-general-info-and-pinout/)), so certain pins are fixed:
 
 * HSPI CLK  = GPIO14
 * HSPI MOSI = GPIO13