Testing the tetraquark structure for the X resonances in the low-lying region Hungchong Kim, K. S. Kim, Myung-Ki Cheoun, Daisuke Jido and Makoto Oka Eur. Phys. J. A, 52 7 (2016) 184 Published online: 05 July 2016 DOI: 10.1140/epja/i2016-16184-0