Columbia subject headings:
Abortion--Congresses.
Chromosome abnormalities--Congresses.
Human chromosome abnormalities--Congresses.
Harvard subject headings:
Abortion--Congresses
Chromosome abnormalities--Congresses.
Human chromosome abnormalities--Congresses.
Princeton subject headings:
Abortion--Congresses.
Chromosome abnormalities--Congresses.
Human chromosome abnormalities--Congresses.