Module level doc

src/libcore/sync/atomic.rs

@@ -21,9 +21,10 @@
 //!
 //! Each method takes an `Ordering` which represents the strength of
 //! the memory barrier for that operation. These orderings are the
-//! same as [LLVM atomic orderings][1].
+//! same as [LLVM atomic orderings][1]. For more information see the [nomicon][2]
 //!
 //! [1]: http://llvm.org/docs/LangRef.html#memory-model-for-concurrent-operations
+//! [2]: https://doc.rust-lang.org/nomicon/atomics.html
 //!
 //! Atomic variables are safe to share between threads (they implement `Sync`)
 //! but they do not themselves provide the mechanism for sharing and follow the