Piezoelastic properties of retgersite determined by ultrasonic measurements D. Arbeck, E. Haussühl, L. Bayarjagal, B. Winkler, N. Paulsen, S. Haussühl and V. Milman Eur. Phys. J. B, 73 2 (2010) 167-175 Published online: 11 December 2009 DOI: 10.1140/epjb/e2009-00423-9