Abstract：Let u=[{S_i, i∈I}]; U, {φ_i, i∈I}] be a amalgam of semigroups, it U_i=U_φ is almost unitary in S_i, for each i in Ⅰ, then the isomorphic copy U~* of U in π_u~* S_i the free product of the semigroup S: amalgamated U, is a relative unitary subsemigrou
1991, Vol. 15 