Abstract. The problem of obtaining characteristics of bound nuclear states from continuum states data is discussed. It is shown that the ambiguities due to the existence of phase-equivalent potentials can be resolved by using the analytic properties of scattering amplitudes. The methods of determination of asymptotic normalization coefficients and vertex constants are considered. The asymptotic normalization coefficients for 6 Li in the α+d channel are found by analytic continuation of the two-channel effective range expansion. The account of inelastic channels within the effective range approach is discussed.