diff --git a/src/Data/Number/Internal.hs b/src/Data/Number/Internal.hs
index f36534a..5a5efd0 100644
--- a/src/Data/Number/Internal.hs
+++ b/src/Data/Number/Internal.hs
@@ -14,7 +14,10 @@ import Data.Number.Types
 import Data.Number.Peano
 import Data.Ratio
 
+-- | Homographic function coefficients matrix
 type Hom   = (Whole, Whole, Whole, Whole)
+
+-- | Bihomographic function coefficients matrix
 type BiHom = (Whole, Whole, Whole, Whole,
               Whole, Whole, Whole, Whole)
 
@@ -60,7 +63,7 @@ absorb (a, b, c, d) x = (a*x + b, a, c*x + d, c)
 
 -- | Bihomographic function
 --
--- Given a 'Hom' matrix
+-- Given a 'BiHom' matrix
 --
 -- <<https://i.imgur.com/Hm7TiIH.png>>
 --