@article {6369,
	title = {Sound speed of a Bose-Einstein condensate in an optical lattice},
	journal = {Physical Review A - Atomic, Molecular, and Optical Physics},
	year = {2008},
	doi = {10.1103/PhysRevA.78.023622},
	author = {Z.X. Liang and Xi Dong and Z.D. Zhang and Biao Wu}
}
