Excerpt from the P.I.E. Guidelines for Authors – Authorship problems and disputes

The two most common authorship problems that may appear are related to gift authorship and ghost authorship. Gift authors refer to persons who fail to meet authorship criteria and had little or no contribution to the article yet are still credited as authors. This can often be because of financial contributions or as an act of favour, and is considered a conscious act of deception. Ghost authorship on the other hand refers to cases where the publisher or editor fails to credit or leaves people out who were active in the research or the writing of the article in question, and crediting the work to another or forgetting them entirely. Both are common causes for disagreement but can more often than not be curtailed through prevention, following the PIE Guidelines, and adhering to a few basic principles of editorial conduct.