Authorship issues in multi-centre clinical trials: the importance of making an authorship contract.

: Discussions about authorship often arise in multi-centre clinical trials. Such trials may involve up to hundreds of contributors of whom some will eventually co-author the final publication. It is, however, often impossible to involve all contributors in the manuscript process sufficiently for them to qualify for authorship as defined by the International Committee of Medical Journal Editors. Therefore, rules for authorship in multi-centre trials are strongly recommended. We propose two contracts to prevent conflicts regarding authorship; both are freely available for use without pay but with reference to the original source.