Chemical substitution and pressure effects in high Tc copper oxide superconductors

In an effort to obtain information concerning the mechanism of superconductivity in the high Tc copper oxide compounds, we have been involved in an extensive investigation of the physical properties of these materials as a function of temperature T, magnetic field H, chemical substitution, and pressure P. Some of the highlights of our recent experiments on the effect of chemical substitution and applied pressure on the electrical resistivity of the high Tc copper oxide superconductors are presented.