The authors   themselves should decide the order in which authors are listed in an   article. No one else knows as well as they do their respective   contributions and the agreements they have made among themselves. Many   different criteria are used to decide order of authorship. Among these   are relative contributions to the work and, in situations where all   authors have contributed equally, alphabetical or random order. Readers   cannot know, and should not assume, the meaning of order of authorship   unless the approach to assigning order has been described by the   authors. Authors may want to include with their manuscript a description   of how order was decided. If so, editors should welcome this   information and publish it with the manuscript.