UPPER CRITICAL FIELD IN Y0.8Ln0.2Ba2Cu3O7-z, Ln = Dy, Er and Tm SUPERCONDUCTORS U. De, S. Kalavathi, T. S. Radhakrishnan et G. V. Subba Rao J. Phys. Colloques, 49 C8 (1988) C8-2167-C8-2168 DOI: 10.1051/jphyscol:19888971