Columbia subject headings:
Agricultural laborers--Colorado.
Agricultural laborers--Michigan.
Child labor--Colorado.
Child labor--Michigan.
Sugar beet industry--Colorado.
Sugar beet industry--Michigan.
Harvard subject headings:
Agricultural laborers--Colorado.
Agricultural laborers--Michigan.
Child labor--Colorado--Statistics.
Child labor--Colorado.
Child labor--Michigan--Statistics.
Child labor--Michigan.
Sugar beet industry--Colorado.
Sugar beet industry--Michigan.
Princeton subject headings: