FREE-PRODUCTS AND 4-DIMENSIONAL CONNECTED-SUMS

We show that a dosed 4-manifold whose fundamental group is a nontrivia l free product is stably homeomorphic to one which admits a correspond ing decomposition into a connected sum, and that connected sums of cop ies of S-1 x S-3 and S-1 ($) over tilde x S-3 may be characterized up to s-cobordism by their fundamental group, Euler characteristic and or ientability. These results are applied to obtain weak splitting and tr iviality theorems for links in S-4.