diff --git a/README.md b/README.md
index 48f8539..64db7ff 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,8 @@
 
 This repository contains the documentations for various CPUs. It contain data sheets, programmer's manuals, quick reference cards, and the like.
 
-Before submitting a pull request, [Contribution Guildelines](contributing.md).
+Before submitting a pull request, please read the [Contribution
+Guildelines](contributing.md).
 
 | Subfolders | Description |
 | ---------- | ----------- |
diff --git a/contributing.md b/contributing.md
index 56be535..7bb71e3 100644
--- a/contributing.md
+++ b/contributing.md
@@ -8,3 +8,6 @@ subdirectory grows large, please add it as a git submodule.  The
 submodule repository should belong to the
 [awesome-cpus](https://github.com/awesome-cpus) origanization.
 Everyone are welcome to join.
+
+Please limit the scope of each commit to one subdirectory, and make
+the first line of the message describe the CPU family.