Ren, Lijuan
He, Dan
Chen, Zhen
Jeppesen, Erik
Lauridsen, Torben L
Søndergaard, Martin
Liu, Zhengwen
Wu, Qinglong L
Article History
Received: 18 February 2016
Revised: 22 September 2016
Accepted: 5 October 2016
First Online: 9 December 2016
Competing interests
: The authors declare no conflict of interest.