From the book; X-Planes.German Luftwaffe Prototypes 1930-1945,
and we must know the MiG I-270 was almost a copy of Me.263,but not advanced fighter,
and we find the work was done by Junkers,although the Ju-248 was not a real development
of it,and its work was stopped in 1944,and in the book they spoke about the works which
still existed in 1945.