provide only the mean-field approximation (MFA) for systems with many distinct stable phases, to present exact results in one dimension and to compare them with MFA For the time-independent growth velocities, Eq. (1), as well as analogous result for homogeneous nucleation, had been previously derived by Bradley and Strenski (BS) for a two-phase nucleation;3 a generalization to arbitrary finite or infinite number of phases is described in Ref. 4. However, BS stressed that Eq.