This should be a doc comment on the method definition in the trait, otherwise, unfortunately, it's not visible in the docs. That is, something like,

```rust
    /// The sum of the samples.
    ///
    /// Note: this method sacrifices performance at the altar of 
    /// accuracy. Depends... [etc.]
    fn sum(self) -> f64;
```

(Also, we might as well cite this properly to help guard against the links going dead (i.e. still make it possible to find the paper), e.g. like [I have been doing in `std::rand`](http://static.rust-lang.org/doc/master/std/rand/distributions/gamma/enum.Gamma.html), so something like `Shewchuk J.R., ["Adaptive Precision Floating-Point Arithmetic and Fast Robust Geometric Predicates"](http://www.cs.cmu.edu/~quake-papers/robust-arithmetic.ps) *Discrete & Computational Geometry 18*, 3 (Oct 1997), 305-363.` ([the page I'm basing this off](http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.71.8830), feel free to use some other citation format.))