Hi ! I have some questions for string specialists. In stringy approaches, the Coleman-Weinberg formula is used to compute the one-loop vacuum amplitude. Such a formula occurs in QFT but also in string models. 1. I am a bit confused with the achievement of the Coleman-Weinberg formula (I know the paper of Coleman and Weinberg, Phys.Rev.D (1973)). Can the paper of Polchinski (Commun. Math. Phys. 104, 37-47 (1986)) be considered as a demonstration of the Coleman-Weinberg formula in string formalism? 2. The Coleman-Weinberg formula is pretty nice since it can be expressed according to the string mass spectrum. Is there a way to keep such a nice expression to compute a one-loop process with two vertices for instance? Are there some papers where such an approach is used? Thank you. Mike.