Author(s): XU Lizhi
Pages: 54
Year: 1984 Issue:  1
Journal: Journal of Mathematical Research and Exposition
Abstract: <正>Let Γ≡(Γ, +,·) be the commutative ring of formal power series with real or complex coefficients, in which the ordinary addition and Cauchy multiplication are defined.Forφ,ψ∈Γ the composition φ(ψ(t) just means a formal substitution of u=ψ(t) into φ(u) in which the operations+and·can be performed indefinitely.We have the following