Gu, Q
Yazdanpanah, M
van Hoek, M
Hofman, A
Gao, X
de Rooij, F W M
Sijbrands, E J G
Article History
Received: 3 March 2014
Revised: 2 June 2014
Accepted: 11 June 2014
First Online: 17 July 2014
Competing interests
: The authors declare no conflict of interest.