Research and non-research articles must cite relevant, timely, and verified (peer-reviewed, where appropriate) literature to support the claims made in the article, so it is mandatory for authors to use a reference manager.

You should avoid excessive and inappropriate self-citation or prior arrangements among groups of authors to inappropriately cite each other's work, as this may be considered a form of misconduct called citation manipulation. Read COPE's guidance on citation manipulation.

If you are the author of a non-research article (e.g. Review or Opinion), you must ensure that the references you cite are relevant and provide a fair and balanced picture of the current state of research or scholarly work on the topic.

Your references should not be biased toward a particular research group, organization, or journal.
If you are unsure whether to cite a source, you should contact the journal's editorial office for advice.

It is important that all references you use are searchable online, so a DOI number for each article is essential.