add link to the buddy_system_allocator

README.md

@@ -11,12 +11,14 @@ eduOS-rs is derived from following tutorials and software distributions:
 1. Philipp Oppermann's [excellent series of blog posts][opp].
 2. Erik Kidd's [toyos-rs][kidd], which is an extension of Philipp Opermann's kernel.
 3. The original version of [eduOS][stlankes], which was the old teaching kernel written in C.
+4. eduOS-rs' uses a memory allocator, which is derived from the [buddy_system_allocator][buddy].
 
 [opp]: http://blog.phil-opp.com/
 [kidd]: http://www.randomhacks.net/bare-metal-rust/
 [stlankes]: http://rwth-os.github.io/eduOS/
 [rust-barebones-kernel]: https://github.com/thepowersgang/rust-barebones-kernel
 [acsos]: http://www.os.rwth-aachen.de/
+[buddy]: https://github.com/rcore-os/buddy_system_allocator
 
 ## Requirements to build eduOS-rs
 eduOS-rs is tested under Linux, macOS, and Windows.