Columbia subject headings:
Astrophysicists--United States--Biography--Congresses.
Draper, Henry, 1837-1882--Congresses.
Orion Nebula--Congresses.
Stars--Formation--Congresses.
Harvard subject headings:
Astrophysicists--United States--Biography--Congresses.
Draper, Henry, 1837-1882--Congresses.
Orion Nebula--Congresses.
Stars--Formation--Congresses
Princeton subject headings:
Astrophysicists--United States--Biography--Congresses.
Draper, Henry, 1837-1882--Congresses.
Orion Nebula--Congresses.
Stars--Formation--Congresses.