FRIES, Simon. A Chronological Bibliography of Latgalian Printed Texts from the 18th to Early 20th Centuries. Rēzekne, Latvia: RTU Rēzeknes akadēmija,2023. Disponível em: https://books.rta.lv/index.php/RTA/catalog/book/28.. Acesso em: 2 apr. 2025.