Contribution to authorship
R Zhou was involved in the conception and planning of the study,
interpretation of the data, and critical revision of the article; Q Xu
was involved in carrying out of the study, writing the first draft and
critical revision of the article; L Ye was involved in the
interpretation of the data, and co-writing of the article; Q-L Wang and
W Xia was involved in acquisition, analysis of the data; X-H Wei was
involved in analysis of the data and revision of the article.