Yazdankhah, M
Farioli-Vecchioli, S
Tonchev, A B
Stoykova, A
Cecconi, F
Article History
Received: 3 June 2014
Revised: 17 July 2014
Accepted: 21 July 2014
First Online: 4 September 2014
Competing interests
: The authors declare no conflict of interest.