Onomastic evidence for the identification of the Asii and Alans is provided by later medieval European scholars and travellers. In the 13th century, Giovanni da Pian del Carpine (Johannes de Plano Carpini) referred to Alani sive Assi ("Alans or Assi") and William of Rubrouck used the name Alani sive Aas ("Alans or Aas").
Medieval European scholars and travelers, particularly in the 13th century, documented evidence for identifying the Asii and Alans.  Giovanni da Pian del Carpine and William of Rubrouck are notable examples who used terms like "Alani sive Assi" and "Alani sive Aas" to refer to these groups.