Columbia subject headings:
Jena (Germany)--Intellectual life--Congresses.
Harvard subject headings:
Abbe, Ernst, 1840-1905--Congresses.
Haeckel, Ernst Heinrich Philipp August, 1834-1919--Congresses.
Jena (Germany)--Intellectual life--Congresses.
Schiller, Friedrich, 1759-1805--Congresses.
Princeton subject headings:
Jena (Germany)--Intellectual life--Congresses.