Both Scarlata and Gingras are concerned that papers by less prominent scientists have disappeared as well without anyone realizing. At a minimum, Gingras wants Planck’s papers restored. “Whoever did it, I don’t care,” he says, “just put them [back] in the database. Intellectually, it’s not acceptable.”

Planck died in 1947, his works are in the public domain in most countries.

1942 titled “Sinn und Grenzen der exakten Wissenschaft” (“Meaning and Limits of Exact Science”), about how to achieve certainty in scientific knowledge, had also appeared in two other journals and been reprinted twice in books. Repackaging the same work multiple times is considered “self-plagiarism” and frowned upon today—the practice produces copyright conflicts and inflates scholars’ publication records. The Naturwissenschaften site gives “copyright violation” as the reason for the retraction.

The papers, both quietly retracted in 2011, originally appeared in the early 1940s in Naturwissenschaften, a German journal now owned by publishing giant Springer Nature