https://books.google.fr/books?id=8IaqthkfLOkC&q=%22Graveur+et+lithographe.+N%C3%A9e+%C3%A0+Li%C3%A8ge+en+1920.%22&dq=%22Graveur+et+lithographe.+N%C3%A9e+%C3%A0+Li%C3%A8ge+en+1920.%22&hl=fr&sa=X&ved=0ahUKEwiTzIyErobgAhUP2xoKHfPoAqcQ6AEIKjAA|id=Le Cabinet des estampes (fr)
https://books.google.fr/books?id=8IaqthkfLOkC&q=%22Graveur+et+lithographe.+N%C3%A9e+%C3%A0+Li%C3%A8ge+en+1920.%22&dq=%22Graveur+et+lithographe.+N%C3%A9e+%C3%A0+Li%C3%A8ge+en+1920.%22&hl=fr&sa=X&ved=0ahUKEwiTzIyErobgAhUP2xoKHfPoAqcQ6AEIKjAA|id=Le Cabinet des estampes (fr)