 Francesco Lanzoni has pointed out that the list of bishops that leads back to Marcian of Tortona is a compilation of the 16th century and that its contents are highly suspect.Additionally, the story of Bishop Marcian depends on a hagiographical source of the 10th century, which is full of anachronisms.Fedele Savio points out that the earliest document referring to Marcian was written between 729 and 820, and that it neither calls Marcian a bishop nor the Bishop of Tortona; and, as he points out, the letter of Bishop Eusebius of Vercelli, written to the people of Tortona from his exile in Scythopolis in 356, makes no mention of a bishop.