Columbia subject headings:
Scientists--Canada--Biography.
Scientists--Canada--Directories.
Scientists--United States--Biography.
Scientists--United States--Directories.
Harvard subject headings:
Scientists--Canada--Biography.
Scientists--Canada--Directories.
Scientists--United States--Biography
Scientists--United States--Directories.
Princeton subject headings:
Scientists--Canada--Biography.
Scientists--Canada--Directories.
Scientists--United States--Biography.
Scientists--United States--Directories.