* Wilfried Feldenkirchen / Eberhard Posner, "The Siemens Entrepreneurs", Continuity and Change, 1847–2005, Ten Portraits, Munich, 2005.
* Wilfried Feldenkirchen / Eberhard Posner, "The Siemens Entrepreneurs", Continuity and Change, 1847–2005, Ten Portraits, Munich, 2005.