  For a metabelian p-group G = <x,y> with two generators x and y, the
annihilator A < Z[X,Y] of the main commutator [y,x] of G, as an ideal of
bivariate polynomials with integer coefficients, is determined by means of a
presentation for G. Furtw\"angler's isomorphism of the additive group
underlying the residue class ring Z[X,Y]/A of Z[X,Y] modulo the annihilator A
to the commutator subgroup G' of G admits the calculation of the abelian type
of G'.
