The Ottone I Diploma
A proclamation of the German Emperor Ottone I (912-973), victorious over Berengario II; granting Udalrico, Count of Carpegna, in 962, the ownership of 27 localities, among which San Marino (clearly cited as "San Marinus").
According to the interpretation of Pochettino in his essay, "San Marino and Mount Titano before 1000 AD", the text of is questionable and therefore lacking any historical value.