  For an algebraically closed field $k$ of characteristic 0, we give a
cycle-theoretic description of the additive 4-term motivic exact sequence
associated to the additive dilogarithm of J.-L. Cathelineau, that is the
derivative of the Bloch-Wigner function, via the cubical additive higher Chow
groups under one assumption. The 4-term functional equation of Cathelineau, an
additive analogue of Abel's 5-term functional equation, is also discussed
cycle-theoretically.
