Issig, S., & Walleston, A. (2019). Kristina Buch: Hans Purrmann - Grosser Preis der Stadt Speyer 2019 / Publisher: City of Speyer, Hans Purrmann Foundation ; catalogue concept: Atelier Issig, Nitschke, Poser / Stefan Issig ; Text: Aimee Walleston. City of Speyer.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रIssig, Stefan, और Aimee Walleston. Kristina Buch: Hans Purrmann - Grosser Preis Der Stadt Speyer 2019 / Publisher: City of Speyer, Hans Purrmann Foundation ; Catalogue Concept: Atelier Issig, Nitschke, Poser / Stefan Issig ; Text: Aimee Walleston. Speyer: City of Speyer, 2019.
एमएलए (8वां संस्करण) प्रशस्ति पत्रIssig, Stefan, और Aimee Walleston. Kristina Buch: Hans Purrmann - Grosser Preis Der Stadt Speyer 2019 / Publisher: City of Speyer, Hans Purrmann Foundation ; Catalogue Concept: Atelier Issig, Nitschke, Poser / Stefan Issig ; Text: Aimee Walleston. City of Speyer, 2019.