Columbia subject headings:
Albert, Hans, 1921---Correspondence.
Philosophers--Germany--Correspondence.
Popper, Karl R. (Karl Raimund), 1902-1994--Correspondence.
Harvard subject headings:
Albert, Hans, 1921---Correspondence.
Philosophers--Germany--Correspondence
Popper, Karl R. (Karl Raimund), 1902-1994--Correspondence.
Princeton subject headings:
Albert, Hans, 1921---Correspondence.
Philosophers--Germany--Correspondence.
Popper, Karl Raimund, Sir, 1902---Correspondence.