Authorship
The uniform requirements for manuscripts submitted to medical journals state that authorship credit should be based only on substantial contribution to:

• conception and design, or analysis and interpretation of data
• drafting the article or revising it critically for important intellectual content
• and final approval of the version to be published. 

All these conditions must all be met. Participation solely in the acquisition of funding or the collection of data does not justify authorship. 

We want authors to assure us that all authors included on a paper fulfil the criteria of authorship. In addition we want assurance that there is no one else who fulfils the criteria but has not been included as an author.

Contributorship
Please note the way that we list the names of contributors to papers published in the BMJ. We believe that the definition of authorship, produced by the International Committee of Medical Journal Editors (or Vancouver Group), has some serious flaws. 

The current definition of authorship does not make clear who has contributed what to the published study, nor does it clarify who is responsible for the overall content. It also excludes those whose sole but often large contribution has been to collect data. 

We now list contributors in two ways. Firstly, we publish a list of authors' names at the beginning of the paper and, secondly, we list contributors (some of whom may not be included as authors) at the end of the paper, giving details of who did what in planning, conducting, and reporting the work. 

One or more of these contributors are listed as guarantors of the paper. The guarantor accepts full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish. See Maintaining the integrity of the scientific record. 

Contributorship and guarantorship are concepts that were applied first to original research papers, and are sometimes hard to define for other articles. Each contributorship statement should make clear who has contributed what to the planning, conduct, and reporting of the work described in the article, and should identify one, or occasionally more, contributor(s) as being responsible for the overall content as guarantor(s). For BMJ articles that do not report original research such as editorials, clinical reviews, and education and debate please state who had the idea for the article, who performed the literature search, who wrote the article, and who is the guarantor (the contributor who accepts full responsibility for the finished article, had access to any data, and controlled the decision to publish). For non-research articles that include case reports such as lessons of the week, drug points, and interactive case reports, please also state who identified and/or managed the case(s).

Researchers must determine among themselves the precise nature of each person's contribution, and we encourage open discussion among all participants. See Authorship is dying; long live contributorship

 Any change in authors and/or contributors after initial submission must be approved by all authors. This applies to additions, deletions, change of order to the authors, or contributions being attributed differently. Any alterations must be explained to the editor. The editor may contact any of the authors and/or contributors to ascertain whether they have agreed to any alteration.