Article History
Accepted: 3 December 2018
First Online: 14 December 2018
Compliance with Ethical Standards
:
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.
: Chau-kiu Cheung declares that he has no conflict of interest. Xiejie Chen declares that she has no conflict of interest. Hoi Yan Cheung declares that she has no conflict of interest.