Minor updates
Typographical changes that do not affect meaning may be corrected in the online version with an updated modification date.
Formal correction
Errors affecting interpretation, attribution or data presentation require a linked correction notice that identifies the change and preserves the original citation.
Retraction
Articles may be retracted when findings are unreliable because of misconduct or major error, publication is redundant, research is unethical or copyright has been seriously breached. The article record and retraction notice will remain accessible and linked.
Expressions of concern
An expression of concern may be issued while a serious matter remains unresolved.