Improved energy of the 21.5 keV M1 + E2 nuclear transition in 151Eu A. Kh. Inoyatov, A. Kovalík, D. V. Filosofov, M. Ryšavý, L. L. Perevoshchikov and A. Baimukhanova Eur. Phys. J. A, 52 5 (2016) 133 Published online: 17 May 2016 DOI: 10.1140/epja/i2016-16133-y