Real and marginal isotope effects in cuprate superconductors
  We critically review recent and earlier results on isotope effects in cuprate superconductors and emphasize that the sample preparation and the isotope exchange and back exchange are crucial in understanding and interpreting the data. Only extremely careful preparation techniques yield reliable results and permit differentiation between real isotope effects and marginal ones. The former are substantial and highlight the lattice vibrational importance in cuprate superconductors. 
A. R. Bishop, A. Bussmann-Holder, O. V. Dolgov, A. Furrer, H.   Kamimura, H. Keller, R. Khasanov, R. K. Kremer, D. Manske, K...