 His original research in this theory is gathered together in his book "Einführung in die algebraische Theorie der Funktionen von zwei Veränderlicher".He also applied his theory to algebraic surfaces (with a presentation of this research in his book "Algebraische Flächen") and worked on birational transformations in the plane (Cremona transformations).During the Weimar Republic, Jung was a member of the anti-republican Alldeutschen Verband and also "Der Stahlhelm".