Also, while you're at it, adding a doc comment along the lines of

```rust
//! Machinery for hygienic macros, as described in the MTWT[1] paper.
//!
//! [1] Matthew Flatt, Ryan Culpepper, David Darais, and Robert Bruce Findler. 2012. *Macros that work together: Compile-time bindings, partial expansion, and definition contexts*. J. Funct. Program. 22, 2 (March 2012), 181-216. DOI=10.1017/S0956796812000093 http://dx.doi.org/10.1017/S0956796812000093 
```

(with more line breaks... ;) )