High Tc superconductivity : notes on achievements and challenges

The intriguing nature of high-Tc superconductivity become evident since the discovery of the new class of oxide superconductors. In this paper some phenomenological evidences mainly related to superconductive tunneling spectroscopy and Josephson effect are discussed. Six years later the state of the art has greatly improved due to the many achievements obtained, however it is not yet suitable for ''last words'' on the matter. Accordingly, the perspective is quite challenging and stimulating. (orig.)