Афанасьевна Морозова, Надежда, and Валерий Чекмонас. “Pious Followers of the Old Faith Near Opočka (Some Socio- and Ethnolinguistic Notes)”. Slavistica Vilnensis, vol. 51, no. 2, Dec. 2002, pp. 93–116, https://www.journals.vu.lt/slavistica-vilnensis/article/view/26845.