United Duchies of Jülich-Cleves-Berg
Initially, his scholarship delved into the early Christian writings, such as his edited epistles of "Macarii Aegyptii epistolæ, homiliarum loci, preces, ad fidem Vaticani, Vindobonensium, Berolinensis," which was published in 1853, and translated into several languages (Modern Greek, Latin, French He was also interested in the emerging Marian phenomenon, and his study of the appearances of Mary, published in 1850, explored the 14th-century manuscripts at the Klosterneuburg (German: Neuburg Priory), near Vienna. He edited documents relating to Ottonian Germany and the papal election of Leo as Pope Leo VIII before the death of Pope John XII in "Die Papstwahl unter den Ottonen" With this, he began a long interest in religious conflict in the lower Rhineland, resulting in several publications relating to the region's religious turmoil, such as the Cologne War and the religious strife in the United Duchies of Jülich-Cleves-Berg.