Unusual behavior of sound velocity of a Bose gas in an optical superlattice at quasi-one-dimension Lei Chen, Zhu Chen, Wu Li, Zhidong Zhang and Zhaoxin Liang Eur. Phys. J. D, 68 12 (2014) 375 Published online: 18 December 2014 DOI: 10.1140/epjd/e2014-50489-3