Electron spin resonance of Eu2+ in the Eu doped clathrate Ba6Ge25J. Sichelschmidt, W. Carrillo-Cabrera, V. A. Ivanshin, Yu. Grin and F. SteglichEur. Phys. J. B, 46 2 (2005) 201-205DOI: https://doi.org/10.1140/epjb/e2005-00246-8