Koester, Helmut, 1926-2016 (Personal Name)

Synoptische Überlieferung bei den apostolischen Vätern, 1957: title page (Helmut Köster)

Introduction to the New Testament, 1982: title page (Helmut Koester)

Harvard Divinity School website, viewed August 16, 2019 (In memoriam Helmut Koester; Helmut Koester, John H. Morison Research Professor of Divinity and Winn Research Professor of Ecclesiastical History; died January 1, 2016; came to Harvard after teaching at the University of Heidelberg from 1956 to 1959) https://hds.harvard.edu/alumni-friends/2016-deans-report/memoriam-helmut-koester

Wikipedia, viewed August 16, 2019 (Helmut Koester; full name: Helmut Heinrich Koester; born December 18, 1926, in Hamburg; died January 1, 2016; German-born American scholar of the New Testament and early Christianity at Harvard Divinity School; research areas: New Testament exegesis; history of early Christianity; and archaeology of the early Christian period; began teaching at Harvard in 1958)