diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2006-2012, Bjorn Buckwalter.
+Copyright (c) 2006-2013, Bjorn Buckwalter.
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/Numeric/Units/Dimensional/TF.lhs b/Numeric/Units/Dimensional/TF.lhs
--- a/Numeric/Units/Dimensional/TF.lhs
+++ b/Numeric/Units/Dimensional/TF.lhs
@@ -55,7 +55,7 @@
 > #-}
 
 > {- |
->    Copyright  : Copyright (C) 2006-2012 Bjorn Buckwalter
+>    Copyright  : Copyright (C) 2006-2013 Bjorn Buckwalter
 >    License    : BSD3
 >
 >    Maintainer : bjorn.buckwalter@gmail.com
@@ -435,10 +435,15 @@
 > one :: Num a => Unit DOne a
 > one = Dimensional 1
 
-For convenience We define some constants for small integer values
-that often show up in formulae. We also throw in 'pi' for good
-measure.
+For convenience we define some constants for small integer values
+that often show up in formulae. We also throw in 'pi' and 'tau' for
+good measure.
 
+The constant for zero is polymorphic as proposed by Douglas McClean
+(http://code.google.com/p/dimensional/issues/detail?id=39) allowing
+it to express zero Length or Capacitance or Velocity etc, in addition
+to the dimensionless value zero.
+
 > _0 :: (Num a) => Quantity d a
 > _0 = Dimensional 0
 
@@ -453,8 +458,12 @@
 > _8 = 8 *~ one
 > _9 = 9 *~ one
 
-> pi :: (Floating a) => Dimensionless a
+For background on 'tau' see http://tauday.com/tau-manifesto (but also
+feel free to review http://www.thepimanifesto.com).
+
+> pi, tau :: (Floating a) => Dimensionless a
 > pi = Prelude.pi *~ one
+> tau = _2 * pi
 
 
 = Instances of 'Show' =
diff --git a/Numeric/Units/Dimensional/TF/NonSI.lhs b/Numeric/Units/Dimensional/TF/NonSI.lhs
--- a/Numeric/Units/Dimensional/TF/NonSI.lhs
+++ b/Numeric/Units/Dimensional/TF/NonSI.lhs
@@ -13,7 +13,7 @@
 otherwise specified.
 
 > {- |
->    Copyright  : Copyright (C) 2006-2012 Bjorn Buckwalter
+>    Copyright  : Copyright (C) 2006-2013 Bjorn Buckwalter
 >    License    : BSD3
 >
 >    Maintainer : bjorn.buckwalter@gmail.com
@@ -72,9 +72,10 @@
 > inch, foot :: Fractional a => Unit DLength a
 > inch = prefix 2.54 (centi meter)
 > foot = prefix 12 inch     -- 0.3048 m
+> mil  = prefix 0.001 inch
 > poundMass, ounce :: Fractional a => Unit DMass a
 > poundMass = prefix 0.45359237 (kilo gram)
-> ounce     = prefix 28.349523 gram
+> ounce     = prefix (1 Prelude./ 16) poundMass
 
 > poundForce :: Fractional a => Unit DForce a
 > poundForce = poundMass * gee  -- 4.4482 N
@@ -168,6 +169,21 @@
 
 > stokes :: (Fractional a) => Unit DKinematicViscosity a
 > stokes = centi meter ^ pos2 / second
+
+
+= Imperial Volumes =
+
+Per http://en.wikipedia.org/wiki/Imperial_units.
+
+> imperialGallon, imperialQuart, imperialPint, imperialCup,
+>                 imperialGill, imperialFluidOunce
+>                 :: (Fractional a) => Unit DVolume a
+> imperialGallon = prefix 4.54609 liter
+> imperialQuart  = prefix (1 Prelude./ 4) imperialGallon
+> imperialPint   = prefix (1 Prelude./ 8) imperialGallon
+> imperialCup    = prefix 0.5 imperialPint
+> imperialGill   = prefix (1 Prelude./ 4) imperialPint
+> imperialFluidOunce = prefix (1 Prelude./ 20) imperialPint
 
 
 = References =
diff --git a/Numeric/Units/Dimensional/TF/Quantities.lhs b/Numeric/Units/Dimensional/TF/Quantities.lhs
--- a/Numeric/Units/Dimensional/TF/Quantities.lhs
+++ b/Numeric/Units/Dimensional/TF/Quantities.lhs
@@ -16,7 +16,7 @@
 dimensionality type synonyms are provided for each quantity type.
 
 > {- |
->    Copyright  : Copyright (C) 2006-2012 Bjorn Buckwalter
+>    Copyright  : Copyright (C) 2006-2013 Bjorn Buckwalter
 >    License    : BSD3
 >
 >    Maintainer : bjorn.buckwalter@gmail.com
@@ -304,6 +304,15 @@
 
 > type DKinematicViscosity = Dim Pos2 Zero Neg1 Zero Zero Zero Zero
 > type KinematicViscosity  = Quantity DKinematicViscosity
+
+> type DFirstMassMoment = Dim Pos1 Pos1 Zero Zero Zero Zero Zero
+> type FirstMassMoment = Quantity DFirstMassMoment
+
+> type DMomentOfInertia = Dim Pos2 Pos1 Zero Zero Zero Zero Zero
+> type MomentOfInertia = Quantity DMomentOfInertia
+
+> type DAngularMomentum = Dim Pos2 Pos1 Neg1 Zero Zero Zero Zero
+> type AngularMomentum = Quantity DAngularMomentum
 
 For these we don't bother defining new type synonyms for dimensionalities.
 Is this rational?
diff --git a/Numeric/Units/Dimensional/TF/SIUnits.lhs b/Numeric/Units/Dimensional/TF/SIUnits.lhs
--- a/Numeric/Units/Dimensional/TF/SIUnits.lhs
+++ b/Numeric/Units/Dimensional/TF/SIUnits.lhs
@@ -11,7 +11,7 @@
 referenced are from [1] unless otherwise specified.
 
 > {- |
->    Copyright  : Copyright (C) 2006-2012 Bjorn Buckwalter
+>    Copyright  : Copyright (C) 2006-2013 Bjorn Buckwalter
 >    License    : BSD3
 >
 >    Maintainer : bjorn.buckwalter@gmail.com
@@ -45,8 +45,8 @@
 >   :: Num a => Unit d a -> Unit d a
 > deka  = prefix 10 -- International English.
 > deca  = deka      -- American English.
-> hecto = deka . deka
-> kilo  = deka . hecto
+> hecto = prefix 100
+> kilo  = prefix 1000
 > mega  = kilo . kilo
 > giga  = kilo . mega
 > tera  = kilo . giga
@@ -60,15 +60,15 @@
 > deci, centi, milli, micro, nano, pico, femto, atto, zepto, yocto
 >   :: Fractional a => Unit d a -> Unit d a
 > deci  = prefix 0.1
-> centi = deci . deci
-> milli = deci . centi
-> micro = milli . milli
-> nano  = milli . micro
-> pico  = milli . nano
-> femto = milli . pico
-> atto  = milli . femto
-> zepto = milli . atto
-> yocto = milli . zepto
+> centi = prefix 0.01
+> milli = prefix 1e-3
+> micro = prefix 1e-6
+> nano  = prefix 1e-9
+> pico  = prefix 1e-12
+> femto = prefix 1e-15
+> atto  = prefix 1e-18
+> zepto = prefix 1e-21
+> yocto = prefix 1e-24
 
 By defining SI prefixes as functions applied to a 'Unit' we satisfy
 section 6.2.6 "Unacceptability of stand-alone prefixes".
@@ -262,9 +262,17 @@
 > tonne     = prefix 1000 (kilo gram) -- Name in original SI text.
 > metricTon = tonne                   -- American name.
 
+In 2012 the IAU redefined the astronomical unit as a conventional
+unit of length directly tied to the meter, with a length of exactly
+149,597,870,700 m and the official abbreviation of au[3].
 
+> astronomicalUnit :: Num a => Unit DLength a
+> astronomicalUnit = prefix 149597870700 meter
+
+
 = References =
 
 [1] http://physics.nist.gov/Pubs/SP811/
 [2] http://en.wikipedia.org/wiki/Minute_of_arc
+[3] http://en.wikipedia.org/wiki/Astronomical_unit
 
diff --git a/dimensional-tf.cabal b/dimensional-tf.cabal
--- a/dimensional-tf.cabal
+++ b/dimensional-tf.cabal
@@ -1,8 +1,8 @@
 Name:                dimensional-tf
-Version:             0.2
+Version:             0.2.1
 License:             BSD3
 License-File:        LICENSE
-Copyright:           Bjorn Buckwalter 2006-2012
+Copyright:           Bjorn Buckwalter 2006-2013
 Author:              Bjorn Buckwalter
 Maintainer:          bjorn.buckwalter@gmail.com
 Stability:           experimental
@@ -23,8 +23,6 @@
     The dimensional-tf packade differs from the dimensional package in that
     the dimension tracking is implemented using type families rather than
     functional dependencies.
-
-    Requires GHC 7.0 or later.
 
 Category:            Math, Physics
 Build-Type:          Simple