diff --git a/README.md b/README.md
index c889b16..9fd2cd8 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@ These are derived from what the [Rust standard library](https://github.com/rust-
 
 - `patterns/` — what to do (error handling, ownership, traits, concurrency, unsafe, macros, etc.)
 - `smells/` — what NOT to do (anti-patterns, common mistakes)
+- `sources/` — reference material from specific projects. Study for ideas, don't copy blindly.
 
 ## How to use
 
@@ -54,6 +55,8 @@ Give your agent these instructions depending on the task:
 
 **Convention** = descriptive. "Project Z does it this way." Context-specific. Study for ideas — applying another project's conventions to yours without understanding their constraints causes harm.
 
+The `sources/` directory is convention material absorbed from specific projects. The `patterns/` directory is what you actually follow.
+
 ## Source
 
 All patterns extracted from `library/` at commit [`f53b654`](https://github.com/rust-lang/rust/tree/f53b654a8882fd5fc036c4ca7a4ff41ce32497a6).