Codex 25 1in the Municipal Library at Porto, Portugal, contains almost exclusively letters ascribed to Saint Jerome. The twelfth-century book mingles letters considered authentically by Jerome with letters doubtfully or wrongly assigned to him. Among the letters in the Porto codex are ten pieces ascribed to Jerome and evidently unpublished. They stand on fols. 101r-104v, 116v-117r and are numbered in the manuscript 151-152, 154-160, and 175.