Richard Van Noorden & Miryam Naddaf

In January, a review paper1 about ways to detect human illnesses by examining the eye appeared in a conference proceedings published by the Institute of Electrical and Electronics Engineers (IEEE) in New York City. But neither its authors nor its editors noticed that 60% of the papers it cited had already been retracted.

The case is one of the most extreme spotted by a giant project to find papers whose results might be in question because they cite retracted or problematic research. The project’s creator, computer scientist Guillaume Cabanac at the University of Toulouse in France, shared his data with Nature’s news team, which analysed them to find the papers that most heavily cite retracted work yet haven’t themselves been withdrawn (see ‘Retracted references’).

“We are not accusing anybody of doing something wrong. We are just observing that in some bibliographies, the references have been retracted or withdrawn, meaning that the paper may be unreliable,” Cabanac says. He calls his tool a Feet of Clay Detector, referring to an analogy, originally from the Bible, about statues or edifices that collapse because of their weak clay foundations.

The IEEE paper is the second-highest on the list assembled by Nature, with 18 of the 30 studies it cites withdrawn. Its authors didn’t respond to requests for comment, but IEEE integrity director Luigi Longobardi says that the publisher didn’t know about the issue until Nature asked, and that it is investigating.