Quantum phase transition in the dioptase magnetic latticeC. Gros, P. Lemmens, K.-Y. Choi, G. Güntherodt, M. Baenitz and H. H. OttoEurophys. Lett., 60 2 (2002) 276-280DOI: https://doi.org/10.1209/epl/i2002-00347-0