The International Committee of Medical Journal Editors (ICMJE) Recommendations list 4 criteria for authorship (http://www.icmje.org/recommendations/browse/roles-and-responsibilities/defining-the-role-of-authors-and-contributors.html):
1) Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND
2) Drafting the work or revising it critically for important intellectual content; AND
3) Final approval of the version to be published; AND
4) Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
In addition to being accountable for the parts of the work he or she has done, an author should be able to identify which co-authors are responsible for specific other parts of the work. In addition, authors should have confidence in the integrity of the contributions of their co-authors.
Those who do not meet all four criteria for authorship should be acknowledged.
The rationale for the four criteria for authorship is to reserve the status of authorship for those who deserve credit and can take responsibility for the work. (Also, authorship confers credit and has important academic, social, and financial implications. Authorship also implies responsibility and accountability for published work.)
The individuals who conduct the work are responsible for identifying who meets these criteria and ideally should do so when planning the work, making modifications as appropriate as the work progresses.
If agreement cannot be reached about who qualifies for authorship, the institution(s) where the work was performed, not the journal editor, should be asked to investigate.
Commentary (by Dexter Leung)
It should be noted that the ICMJE Recommendations are primarily addressed to the editors of medical journals. Nonetheless, they may be of interest to researchers in other disciplines as they are cited in the Office of Research Integrity’s Introduction to the Responsible Conduct of Research, a document which is expressly referred to in the HKU Policy on Research Integrity.