We show that the equations derived by LeBrun to describe scalar-flat K
ahler surfaces with a conformal S1-action are the continuous long wave
approximation for the Toda-type system associated with the semi-direc
t sum of the algebra A(r) and the commutive multiplet which transforms
according to the adjoint representation of A(r). Moreover, we display
the corresponding continuum Lie algebra, on which the Maurer-Cartan 1
-form (written explicitly) takes values for the equations under consid
eration, the improved energy-momentum tensor, etc.