The published record is permanent. When something is wrong with an article, the journal issues a public notice rather than editing or deleting it.

Which notice applies

• Correction - an error that does not affect the findings or conclusions. The article remains valid and is linked to the notice.
• Expression of concern - a credible concern has been raised and an investigation is under way. Published while the outcome is unknown.
• Retraction - the findings are unreliable, whether through honest error or misconduct. The article stays online, clearly marked as retracted, with the reason stated.

Journals differ in how they distinguish an author error from a publisher error; here the notice states plainly what happened and who identified it.

Raising a concern

Write to the editorial office with the article identifier and the specific concern. Concerns are acknowledged and investigated; the outcome is communicated to the person who raised it.