diff --git a/Data/Matrix.hs b/Data/Matrix.hs
--- a/Data/Matrix.hs
+++ b/Data/Matrix.hs
@@ -90,6 +90,11 @@
   (q,r) = quotRem k m
 
 -- | Type of matrices.
+--
+--   Elements can be of any type. Rows and columns
+--   are indexed starting by 1. This means that, if @m :: Matrix a@ and
+--   @i,j :: Int@, then @m ! (i,j)@ is the element in the @i@-th row and
+--   @j@-th column of @m@.
 data Matrix a = M {
    nrows :: {-# UNPACK #-} !Int -- ^ Number of rows.
  , ncols :: {-# UNPACK #-} !Int -- ^ Number of columns.
@@ -116,7 +121,7 @@
 
 -- | /O(rows*cols)/. Similar to 'V.force', drop any extra memory.
 --
---   Useful when using 'submatrix' from a big matrix.
+--   Useful when using 'getRow' from a big matrix.
 forceMatrix :: Matrix a -> Matrix a
 forceMatrix (M n m v) = M n m $ V.force v
 
@@ -231,16 +236,24 @@
 fromList n m = M n m . V.fromListN (n*m)
 
 -- | Create a matrix from an non-empty list of non-empty lists.
---   /Each list must have the same number of elements/.
---   For example:
+--   /Each list must have at least as many elements as the first list/.
+--   Examples:
 --
 -- > fromLists [ [1,2,3]      ( 1 2 3 )
 -- >           , [4,5,6]      ( 4 5 6 )
 -- >           , [7,8,9] ] =  ( 7 8 9 )
 --
+-- > fromLists [ [1,2,3  ]     ( 1 2 3 )
+-- >           , [4,5,6,7]     ( 4 5 6 )
+-- >           , [8,9,0  ] ] = ( 8 9 0 )
+--
 fromLists :: [[a]] -> Matrix a
 {-# INLINE fromLists #-}
-fromLists xss = fromList (length xss) (length $ head xss) $ concat xss
+fromLists [] = error "fromLists: empty list."
+fromLists (xs:xss) = fromList n m $ concat $ xs : fmap (take m) xss
+  where
+    n = 1 + length xss
+    m = length xs
 
 -- | /O(1)/. Represent a vector as a one row matrix.
 rowVector :: V.Vector a -> Matrix a
@@ -346,14 +359,14 @@
 {-# INLINE unsafeMset #-}
 unsafeMset x m p v = MV.unsafeWrite v (encode m p) x
 
--- | /O(1)/. Replace the value of a cell in a matrix.
+-- | Replace the value of a cell in a matrix.
 setElem :: a -- ^ New value.
         -> (Int,Int) -- ^ Position to replace.
         -> Matrix a -- ^ Original matrix.
         -> Matrix a -- ^ Matrix with the given position replaced with the given value.
 setElem x p (M n m v) = M n m $ V.modify (msetElem x m p) v
 
--- | /O(1)/. Unsafe variant of 'setElem', without bounds checking.
+-- | Unsafe variant of 'setElem', without bounds checking.
 unsafeSet :: a -- ^ New value.
         -> (Int,Int) -- ^ Position to replace.
         -> Matrix a -- ^ Original matrix.
@@ -378,6 +391,11 @@
 -- >                ( 1 2 3 )   ( 4 5 6 0 0 )
 -- >                ( 4 5 6 )   ( 7 8 9 0 0 )
 -- > extendTo 0 4 5 ( 7 8 9 ) = ( 0 0 0 0 0 )
+--
+-- The definition of 'extendTo' is based on 'setSize':
+--
+-- > extendTo e n m a = setSize e (max n $ nrows a) (max m $ ncols a) a
+--
 extendTo :: a   -- ^ Element to add when extending.
          -> Int -- ^ Minimal number of rows.
          -> Int -- ^ Minimal number of columns.
@@ -435,7 +453,7 @@
 minorMatrix r c (M n m v) =
  M (n-1) (m-1) $ V.ifilter (\k _ -> let (i,j) = decode m k in i /= r && j /= c) v
 
--- | Make a block-partition of a matrix using a given element as reference.
+-- | /O(rows*cols)/. Make a block-partition of a matrix using a given element as reference.
 --   The element will stay in the bottom-right corner of the top-left corner matrix.
 --
 -- >                 (             )   (      |      )
@@ -463,8 +481,12 @@
 splitBlocks i j a@(M n m _) = ( submatrix    1  i 1 j a , submatrix    1  i (j+1) m a
                               , submatrix (i+1) n 1 j a , submatrix (i+1) n (j+1) m a )
 
-
--- | Join blocks of the form detailed in 'splitBlocks'.
+-- | Join blocks of the form detailed in 'splitBlocks'. Precisely:
+--
+-- > joinBlocks (tl,tr,bl,br) =
+-- >   (tl <|> tr)
+-- >       <->
+-- >   (bl <|> br)
 joinBlocks :: (Matrix a,Matrix a,Matrix a,Matrix a) -> Matrix a
 joinBlocks (tl,tr,bl,br) = (tl <|> tr)
                                <->
@@ -506,7 +528,7 @@
 -------------------------------------------------------
 ---- MATRIX OPERATIONS
 
--- | Perform an operation elementwise. The input matrices are assumed
+-- | Perform an operation element-wise. The input matrices are assumed
 --   to have the same dimensions, but this is not checked.
 elementwise :: (a -> b -> c) -> (Matrix a -> Matrix b -> Matrix c)
 elementwise f (M n m v) (M _ _ v') = M n m $ V.zipWith f v v'
diff --git a/matrix.cabal b/matrix.cabal
--- a/matrix.cabal
+++ b/matrix.cabal
@@ -1,5 +1,5 @@
 Name: matrix
-Version: 0.3.1.0
+Version: 0.3.1.1
 Author: Daniel Díaz
 Category: Math
 Build-type: Simple