Resumen de On the Early History of Perfective 'Present' Participles in East Slavic
Birchbark letters from Novgorod from the 11th and 12th centuries show distinctions in the use of the two perfective active participles in Old Russian, a distinction thought to have been lost very early. Examination of the use of these participles in chronicles shows that the loss of this distinction began in the South in the 11th century, became more prevalent there in the 12th, but did not affect the Novgorod Chronicle until the late 12th century, so the Birchbark data are not surprising
