Columbia subject headings:
Algebraic topology--Congresses.
Differential equations--Congresses.
Geometry, Algebraic--Congresses.
Lefschetz, Solomon, 1884-1972.
Harvard subject headings:
Algebraic topology--Congresses.
Differential equations--Congresses.
Geometry, Algebraic--Congresses.
Lefschetz, Solomon, 1884-1972
Princeton subject headings:
Algebraic topology--Congresses.
Differential equations--Congresses.
Geometry, Algebraic--Congresses.
Lefschetz, Solomon, 1884-1972.