Episcopal letter of Nathan Söderblom, Archbishop of Uppsala
MLA style: "Nathan Söderblom - Nobel Lecture: The Role of the Church in Promoting Peace".
http://www.nobelprize.org/nobel_prizes/peace/laureates/1930/soderblom-lecture.html
Jonas Jonson, Nathan Söderblom. Called to Serve, Grand Rapids (Michigan), William B. Eerdmans Publishing Company, 2016.