Internet movie database, Sept. 27, 2002 (Douglas Sirk; birth name, Claus Detlef Sierck; b. Apr. 26, 1900 in Hamburg, Germany; sometimes credited as Detlef Sierck, Detlev Sierck)
IMDb, July 27, 2005 (Douglas Sirk; b. Apr. 26, 1897, Hamburg, Germany; d. Jan. 14, 1987, Lugano, Switzerland; sometimes credited as Detlef Sierck, Detlev Sierck; birth name: Hans Detlef Sierck; director, writer, producer)
Information from 678 converted Dec. 17, 2014 (orig. name: Hans Detlef Sierck)