Columbia subject headings:
Engineers--Employment--United States--Statistics--Periodicals.
Industrial technicians--Employment--United States--Statistics--Periodicals.
Scientists--Employment--United States--Statistics--Periodicals.
Harvard subject headings:
Princeton subject headings:
Engineers--Employment--United States--Statistics--Periodicals.
Industrial technicians--Employment--United States--Statistics--Periodicals.
Periodicals.
Scientists--Employment--United States--Statistics--Periodicals.
Statistics.