The scale of the problem
An analysis by researchers at Columbia University, reported by Retraction Watch in May 2026, found that about 1 in 277 PubMed-indexed papers from early 2026 cited a reference that does not exist, up from about 1 in 2,828 in 2023. Preprint servers have responded as well: arXiv has said it may ban authors for a year when there is clear evidence they did not check LLM-generated content, including hallucinated references.
What existing reference checkers do, and what they leave out
Several free tools already check whether a reference exists in a bibliographic database. That is useful, and Checked Sources does not try to replace it. What those tools do not produce is a record of the author's own verification: that each source was opened, that each quotation was read against the original, and when.
What Checked Sources is designed to provide
- A review queue built from a thesis, paper or report, including quotations and web sources
- DOI lookup to confirm that cited papers exist
- A finding recorded for each source, with notes on corrections made
- A verification statement that can be shared with an advisor, committee or editor
Quotations and web sources, not only references
Reference checkers work from the bibliography. Many errors are elsewhere: a quotation that drifted from the original wording, a statistic attributed to the wrong report, or a web page that has changed since it was cited. Checked Sources is designed to work from the full text of the document, so a quotation is checked against the page it came from and a web source is checked as it stands on the day of review, with a capture of what was seen.
A record that speaks for your work
AI-writing detectors give a probability, not evidence, and they can misjudge careful human writing. A record of how you verified your sources is a different kind of answer. It shows the work you did, in the order you did it.
A student plan is planned for single theses and papers. See plans.