To understand matter from a point of view of clusters X.-Y. Shen, Y.-G. Xu, C.-L. He, H.-T. Liu and J.-M. Li Eur. Phys. J. D, 34 1-3 (2005) 109-112 Published online: 13 July 2005 DOI: 10.1140/epjd/e2005-00130-9