Dr. Speners explanation of Christian Doctrine
attached to a PB this CN will maybe seem odd. But maybe not.
Schmidt's book on the scriptural Character of the Lutheran doctrine of the Lord's Supper references "Dr. Philipp Jacob Spener’s einfache Erklærung der christlichen Lehre nach der Ordnung des kleinen Katechismus Luthers in Fragen und Antworten verfasst und mit noethigen Zeugnissen der Schrift bewæhrt."
The German language edition of Spener's book was reprinted in 1984 in modernized German, the section cited starts with question 1099 on page 357.