Zhang, Hai-Tao
Chen, Zhiyong
Vicsek, Tamás
Feng, Guanjun
Sun, Longsheng
Su, Riqi
Zhou, Tao
Article History
Received: 7 August 2013
Accepted: 23 June 2014
First Online: 24 July 2014
Competing interests
: The authors declare no competing financial interests.