Thomas Prügl from the Universität Wien (link) writes to us with this question:

Let me use the expertise of Thomistica to ask a question: Some months ago, I read a note about a study that included an English translation of the Liber de fide trinitatis, the famous "Libellus" that Pope Urban asked Saint Thomas to examine and that became the occasion for Aquinas' Contra errores graecorum. Father Dondaine edited the Libellus in vol. 40 of the Leonine Edition, along with Contra errores graecorum. Unfortunately I did not wirte down the author and the title, but does anybody know this study or translation?

Please feel free to offer suggestions in the Comments section below, or write to Dr Prügl here.

PS: I checked Fr. Joseph Kenny's library of texts on this but came up short. Any ideas?