1.
Dirk Christiaan Hesseling an Hugo Schuchardt (07-04684)
2.
Dirk Christiaan Hesseling an Hugo Schuchardt (08-04685)
Dirk Christiaan Hesseling an Hugo Schuchardt (09-04686)
Dirk Christiaan Hesseling an Hugo Schuchardt (11-04688)
Dirk Christiaan Hesseling an Hugo Schuchardt (12a-04689a)
Julio de Urquijo Ybarra an Hugo Schuchardt (064-12041)
Julio de Urquijo Ybarra an Hugo Schuchardt (264-12141)
Hugo Schuchardt an Reinhold Köhler (011-S.23-25)
Reinhold Köhler an Hugo Schuchardt (012-05693)
Hugo Schuchardt an Reinhold Köhler (138-S.273-274)