  We present the new expressions for the formfactors of local operators for the
XX - quantum spin chain as a Cauchy determinants. Using the known functional
form of the correlator at large distances we propose the new expression for the
constant for the asymptotics of the correlator as a Cauchy determinant. We
calculate the momentum distribution for the general case of the XXZ spin chain
and point out that it is completely different from the Luttinger model (the
system of fermions). For the XX chain we compare numerically the value of the
lowest formfactor and the expectation value of momentum- zero operators which
is determined by the functional form of the correlator.
