Yersin, Hartmut and Huber, P. and Gietl, G. and Trümbach, D. (1992) Pressure-induced tuning of fluorescence to phosphorescence in [Cr(urea-h₄)₆](ClO₄)₃ and [Cr(urea-d₄)₆](ClO₄)₃. Chemical Physics Letters 199 (1-2), pp. 1-9.