U. Hummel, T. Telaumbanua: Independent Churches on Nias and the Batu Islands (1930-1965). Cross and Adu: A Socio-Historical Study on the Encounter between Christianity and the Indigenous Culture on Nias and the Batu Islands, Indonesia (1865–1965)]. Dissertationsschrift, Universität Utrecht, 2007 (Niederlande). Kapitel 5, Seite 193