Most of Contreni’s scholars can be geographically located because we know the institutions with which they were affiliated. The letters themselves more often than not begin with an address mentioning the name, rank and affiliation of both the sender and recipient.
Diagram 3 locates Contreni’s scholars on a map of Europe (custom constructed using Tableau). 
The names in red are the senders of the letters studied by Contreni; those in green the recipients. Arrows linking individuals show the direction of correspondence. Alcuin as abbot of Tours, Lupus as abbot of Ferrières, and Hrabanus as abbot of Fulda are rendered in larger letters. Less easy to read in this rendition are those places emerging as important focal points in the Carolingian intellectual network. Notice the cluster of scholars at Fulda, for example: Hrabanus, Rudolf, Ercanbert and Meginhard; the smaller cluster at Corbie of Ratramnus and Hildemar.
But the act of placing an individual on a map involves in some cases guesswork, in most cases, choice. Some correspondents—the gaggle of students associated with Alcuin, for example—are impossible to place. They float on this map, unmoored from any particular institution. In contrast, many of the scholars represented here were associated at one time or another with several places. The Carolingian educational system allowed gifted young monks and clerics to travel and study with masters outside their own institutions, for example. This is how Hrabanus came to be a student of Alcuin, traveling first to Charlemagne’s court in Aachen, then making a second trip to Tours before returning to Fulda (see Diagram 4). It is how Lupus came to be a student of Hrabanus, traveling from Ferrières to Fulda where he remained for about seven years before returning to his home monastery. From Ferrières Lupus made additional trips to Aachen, to the court of Charlemagne’s successor, the Emperor Louis the Pious. Monks like Lupus traveled. Not all of the letters composed by Lupus and represented on this map were written at Ferrières. Some—those to Einhard whom I’ve placed in Seligenstadt—were written while he was Hrabanus’s student at Fulda. The map has simplified a situation that was more dynamic and complex, but in doing so it reflects the common practice of labeling individuals according to the place with which they had the closest (or longest) association: hence medievalists routinely refer to Lupus as “Lupus of Ferrières.”
In reality most of the men on this map had multiple associations: Gottschalk “of Orbais,” for example, started out his career as a monk at Fulda, and can be counted among Hrabanus’s many students. But Orbais is only one out of many places that hosted him over the course of his troubled life. Christian “of Stavelot” began his career as a monk at Corbie, as did Odo, later Bishop of Beauvais. Arn, Bishop of Salzburg, and probably one of Alcuin’s closest friends (to judge from the large number of letters Alcuin wrote to Arn) was also abbot of St. Amand, a monastery much closer to Tours than Salzburg. If we are to do justice to the networks these men forged and maintained, we ought to be able to take account of their multiple associations. Text-based scholarship, for clarity’s sake, must needs fall back on familiar labels (rather like the modern practice of using surnames). Digital representations of networks need to find more dynamic solutions.