Columbia subject headings:
Agricultural laborers--Mexico.
Agricultural laborers--United States.
Mexico--Emigration and immigration.
United States--Emigration and immigration.
Harvard subject headings:
Agricultural laborers--Mexico
Agricultural laborers--United States
Mexico--Emigration and immigration.
United States--Emigration and immigration.
Princeton subject headings:
Agricultural laborers--Mexico.
Agricultural laborers--United States.
Mexico--Emigration and immigration.
United States--Emigration and immigration.