2014-01-08:
  On page 29, in the formula for A_Delta(t), there is a minus (-) missing
  in front of the first term in the inner block.  Instead of

    A_Delta(t) = 1/2 * (  t^2 * (   s1y s2x + s1x s2y + s1y s3x ...

  It should read:

    A_Delta(t) = 1/2 * (  t^2 * ( - s1y s2x + s1x s2y + s1y s3x ...
                                 ^^^
  Thanks to David Geier.