Title: Order of superconductive phase transition
Authors: H.Kleinert (Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany)

On the occasion of Reinhard Folk's 60th birthday, I give a brief review of the theoretical progress in understanding the critical properties of superconductors. I point out the theoretical difficulties in finding a second-order transition in the Ginzburg-Landau Model with O(N)-symmetry in 4-ε Dimensions, and the success in predicting the existence and location of a tricritical point with the help of a dual disorder theory.

Key words: superconductivity, phase transitions, renormalization group
PACS: 05.70.Jk, 64.60.Fr, 74.20.-z