diff --git a/fw/rtl/external/README.md b/fw/rtl/external/README.md
index 0e296fd..8cd088b 100644
--- a/fw/rtl/external/README.md
+++ b/fw/rtl/external/README.md
@@ -8,6 +8,10 @@ This folder contains code downloaded directly from external repositories with mi
 
 [https://github.com/ZipCPU/qspiflash/blob/master/rtl/qflexpress.v](https://github.com/ZipCPU/qspiflash/blob/master/rtl/qflexpress.v)
 
+### Documentation
+
+There's [comprehensive documentation](https://zipcpu.com/blog/2019/03/27/qflexpress.html) for this module:
+
 ### Modifications
 
 - Changed initialization sequence.
@@ -21,5 +25,5 @@ This folder contains code downloaded directly from external repositories with mi
 
 ### Modifications
 
-- Changed refresh interval that suits 90 MHz clock and used SDRAM.
+- Changed refresh interval that suits 90 MHz clock and used SDRAM chip.
 - Changed column and row address widths.