Fokidis, M. (2013). Helmut Middendorf: Observer ; collagen & drawings / [Editor:] Eleni Koroneou Gallery. Text: Marina Fokidis. Kerber Verlag.
Chicago-referens (17:e uppl.)Fokidis, Marina. Helmut Middendorf: Observer ; Collagen & Drawings / [Editor:] Eleni Koroneou Gallery. Text: Marina Fokidis. Bielefeld ; Berlin: Kerber Verlag, 2013.
MLA-referens (8:e uppl.)Fokidis, Marina. Helmut Middendorf: Observer ; Collagen & Drawings / [Editor:] Eleni Koroneou Gallery. Text: Marina Fokidis. Kerber Verlag, 2013.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.