Article History
Received: 17 July 2019
Accepted: 23 September 2019
First Online: 20 November 2019
Ethics approval and consent to participate
: Ethical approval is not necessary because it is a comment on previously published articles and does not involve the handing of any personal patient data.
: Not applicable.
: Zhenxiong JIN, Jinman CHEN, Bing SHU, Yanhua XIAO and Dezhi TANG declare that they have no conflict of interest.