The Holy See's Interest in Estonia in the 1920s and 1930s - Ketola, Mikko (. The @Holy See's Foreign Policies in Inter-War Europe. - Helsinki : Suomen Kirkkohistoriallinen Seura, 2016. - 207 Seiten. - Diagramme, Karte. - ISBN 978-952-5031-85-0, 2016)