diff --git a/CS/Languages/Rust.md b/CS/Languages/Rust.md
index 2ae08fa..7fc6d3c 100644
--- a/CS/Languages/Rust.md
+++ b/CS/Languages/Rust.md
@@ -16,4 +16,8 @@ tags:
 
 ## Rayon
 [https://crates.io/crates/rayon](https://crates.io/crates/rayon)
--   Data parallelism
\ No newline at end of file
+-   Data parallelism
+
+# FFI
+[How to implement long-lived variables/state in a library?](https://stackoverflow.com/questions/59028838/how-to-implement-long-lived-variables-state-in-a-library)
+[Foreign Function Interface - Rustonomicon](https://doc.rust-lang.org/nomicon/ffi.html#foreign-function-interface)