Based on the ICMJE guidelines for authorship criteria, what you need to do is clarify how each author has contributed to the paper. Authorship credits should be based on following several main items:
Conception or design of the work
Data analysis and interpretation
Drafting the article
Critical revision of the article
Final approval of the version to be published
Please mention the contribution made by each author, including above several mian points or other specific work.
If the editors judged that anyone in the author list has no substantial contribution to this work, they have the right to ask the corresponding author to justify or delete the name/s.
Corresponding author bears the full legal responsibility for the correctness of the contribution declared by each author.
Note that the names of all the co-authors should be written for the last point. Once you draft the contributorship statement, make sure to get it signed by all the co-authors before you submit it to the journal.
Please download Author Contribution and Agreement Form, which should be signed by all author(s) when you submit your works to our journal.