Each author should have made sufficient scientific contribution to the article in order to take public responsibility for the content. Authorship credit should be assigned only on substantial input to:
• conception and design of the study,
• analysis and interpretation of data,
• writing a major portion of the paper,
• critically revising the paper and
• final approval of the version to be published.
Authors are listed in the by-line. Individuals who do not meet the criteria for authorship may be listed in the acknowledgements section of the manuscript. Such contributions may include funds collection, recruiting participants, collecting or entering the data, etc.
You can find Authorship Statement Form here. It must be sign by all authors which participate in manuscript writing and submission.