He became a member of the Berlin Academy of Sciences in 1884, and in 1886, after the death of Georg Waitz, undertook the supervision of the Leges section of the Monumenta Germaniae Historica.
Hanover: Monumenta Germaniae Historica, Scriptores Rerum Germanicarum In Usum Scholarum Separatim Editi, vol.
He was a member of the American Academy of Arts and Sciences, the American Philosophical Society, the Pontificia Accademia Romana di Archeologia (since 1990 Hon. Mem.), The German Archaeological Institute, the Zentraldirektion of the Monumenta Germaniae Historica.
Among the IHR’s extensive collection of books on European history are a set of volumes of the Monumenta Germaniae Historica donated to the University of London by the Nazi government of Germany in 1937.
The letter, published in Monumenta Germaniae Historica and usually referred to as Dei patris immensa, suggests that his mission was primarily religious in character.
It has been frequently published — first by Chifflet in André Duchesne's Historiæ Francorum Scriptores, I (1636), 210-214; again by Migne in Patrologia Latina, LXXII, 793-802, by Theodor Mommsen in Monumenta Germaniae Historica, Auctores antiqui, XI (1893), 232-9, and by Justin Favrod with a French translation: La chronique de Marius d'Avenches (455–581) (Lausanne 1991).
His most recent publication is a book on the seventh- and eighth-century versions of the Chronicle of Fredegar for the Monumenta Germaniae Historica.