Structural investigations of the tetraborates MB4O7 (M = Pb, Sr, Ba)W.-D. Stein, J. Liebertz, P. Becker, L. Bohatý and M. BradenEur. Phys. J. B, 85 7 (2012) 236DOI: https://doi.org/10.1140/epjb/e2012-21062-y