diff --git a/README.md b/README.md
index bdcbc03..e2dccc1 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,8 @@
 Implementation of TrueSkill™ in Rust.
 
 ## See
+
 * [mafredri/go-trueskill](https://github.com/mafredri/go-trueskill)
 * [JesseBuesking/trueskill](https://github.com/JesseBuesking/trueskill)
 * [sublee/trueskill](https://github.com/sublee/trueskill)
+* [moserware/Skills](https://github.com/moserware/Skills)
diff --git a/src/lib.rs b/src/lib.rs
index cd23273..911d1bb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,11 +27,58 @@ const DRAW_PROBABILITY: f64 = 0.10;
 ///  A basis to check reliability of the result.
 const DELTA: f64 = 0.0001;
 
+pub trait Rateable {
+    fn mu(&self) -> f64;
+    fn sigma(&self) -> f64;
+}
+
+#[derive(Debug, PartialEq)]
+pub struct Rating {
+    pub mu: f64,
+    pub sigma: f64,
+}
+
+impl Rating {
+    pub fn new(mu: f64, sigma: f64) -> Rating {
+        Rating { mu, sigma }
+    }
+}
+
+impl Rateable for Rating {
+    fn mu(&self) -> f64 {
+        self.mu
+    }
+
+    fn sigma(&self) -> f64 {
+        self.sigma
+    }
+}
+
+impl Rateable for Gaussian {
+    fn mu(&self) -> f64 {
+        self.mu()
+    }
+
+    fn sigma(&self) -> f64 {
+        self.sigma()
+    }
+}
+
 fn draw_margin(p: f64, beta: f64, total_players: f64) -> f64 {
     math::icdf((p + 1.0) / 2.0) * total_players.sqrt() * beta
 }
 
-pub fn rate(rating_groups: &[&[Gaussian]]) {
+/*
+pub fn calculate_ratings<R>(team_players: &[R], team_ranks: &[u16]) -> Vec<Rating>
+where
+    R: Rateable,
+{
+*/
+
+pub fn rate<R>(rating_groups: &[&[R]]) -> Vec<Rating>
+where
+    R: Rateable,
+{
     let flatten_ratings = rating_groups
         .iter()
         .flat_map(|group| group.iter())
@@ -171,7 +218,7 @@ pub fn rate(rating_groups: &[&[Gaussian]]) {
         factor.update_mean(&mut variable_arena);
     }
 
-    println!("after:");
+    let mut ratings = Vec::new();
 
     for i in 0..size {
         let value = variable_arena
@@ -179,11 +226,13 @@ pub fn rate(rating_groups: &[&[Gaussian]]) {
             .map(|variable| variable.get_value())
             .unwrap();
 
-        let mu = value.mu();
-        let sigma = value.sigma();
-
-        println!("* player={}, mu={}, sigma={}", i, mu, sigma);
+        ratings.push(Rating {
+            mu: value.mu(),
+            sigma: value.sigma(),
+        });
     }
+
+    ratings
 }
 
 pub fn quality(rating_groups: &[&[Gaussian]]) -> f64 {
@@ -262,8 +311,13 @@ mod tests {
         let chris = Gaussian::from_mu_sigma(MU, SIGMA);
         let darren = Gaussian::from_mu_sigma(MU, SIGMA);
 
-        rate(&[&[alice], &[bob], &[chris], &[darren]]);
+        let new_ratings = rate(&[&[alice], &[bob], &[chris], &[darren]]);
 
-        assert_eq!(true, false);
+        assert_eq!(new_ratings, vec![
+            Rating::new(33.20778932559525, 6.347937214998893),
+            Rating::new(27.401497882797486, 5.787057812482782),
+            Rating::new(22.598576351652632, 5.7871159419307645),
+            Rating::new(16.79337409436942, 6.348053083319977),
+        ]);
     }
 }