Why Non-Peer-Reviewed Sources Need Special Treatment

When you cite a peer-reviewed journal article, readers can assume it passed editorial scrutiny. Preprints, working papers, and similar sources haven't gone through that process—which doesn't make them invalid, but does make transparency essential.

Your citation needs to clearly signal that this source has a different status than a published journal article.

Types of Non-Peer-Reviewed Sources

Preprints are complete manuscripts shared publicly before (or instead of) peer review. Common platforms include arXiv (physics, math, CS), bioRxiv and medRxiv (biology, medicine), SSRN (social sciences, law), and PsyArXiv (psychology).

Working papers are in-progress research, often shared through institutional series (NBER, World Bank, university departments). They may eventually become journal articles.

Conference papers vary widely—some conferences have rigorous peer review, others accept based on abstracts only. Know your field's norms.

Theses and dissertations are reviewed by committees but not through journal peer review. They're generally treated as credible academic sources with their own citation format.

Technical reports from organizations, government agencies, or research institutes also fall outside traditional peer review.

General Principles Across All Styles

Regardless of citation format, you need to clearly identify the source type. Don't let readers assume something is peer-reviewed when it isn't. Include the repository or platform name (arXiv, SSRN, etc.), include any version numbers or identifiers, include the date posted or last revised, and use the DOI if one exists.

If a preprint has since been published, cite the published version instead—unless you're specifically discussing the preprint itself or changes between versions.

Quick Reference by Major Style

APA (7th Edition) treats preprints as a specific source type:

Author, A. A. (Year). Title of preprint. PsyArXiv. https://doi.org/xxxxx

Include "Advance online publication" if accepted but not yet published. Use the preprint server name in italics where you'd normally put the journal name.

MLA (9th Edition) includes the platform as the container:

Author. "Title of Preprint." arXiv, version number, date, doi or URL.

Chicago treats preprints similarly to unpublished manuscripts:

Author. "Title." Preprint, submitted date. Platform. DOI or URL.

IEEE uses the standard conference/report format with the preprint server as the source.

The exact formatting varies, so check the specific style guide for your discipline.

Working Papers: Extra Considerations

Working papers often have series numbers (e.g., "NBER Working Paper No. 28374"). Always include these—they're how readers will find the document.

The issuing institution matters: an NBER working paper carries different weight than an unknown departmental series. Include enough information for readers to assess the source's credibility.

Should You Cite Preprints at All?

This is a legitimate question. Some considerations:

Arguments for: Research moves fast, preprints establish priority, waiting for publication can take years, and preprints are increasingly accepted in many fields.

Arguments against: No peer review means errors may not be caught, preprints can be revised or withdrawn, and some fields (humanities especially) still treat preprints as preliminary.

Best practice: Preprints are appropriate for establishing that someone is working on a topic, citing very recent findings in fast-moving areas, and your own field norms accept them. Preprints are risky for foundational claims your argument depends on heavily, fields where peer review is expected for all cited sources, and work that might be revised substantially.

When possible, pair preprint citations with peer-reviewed sources making similar points.

What If the Preprint Gets Published?

Update your citation to the published version before submission. This is standard practice. If you're citing a specific element that changed between versions, you might cite both—the preprint for the original claim and the published version for the revision.

If the preprint is withdrawn or retracted, remove the citation entirely unless you're specifically discussing the retraction.

The Version Problem

Preprints can be updated. A paper posted in January might be revised in June. This creates two issues.

First, page numbers may change between versions. If you're citing a specific page, note the version.

Second, content may change. Something you cited might be revised or removed. Check for updates before final submission.

Most repositories use version numbers (v1, v2) or dates. Include this information in your citation.

The exact formatting for preprint citations depends on your required citation style. Check the specific guide for your discipline below.