1939

Steibling's standard of essential nutrients from 1933 is expanded to include thiamine and riboflavin. Separate recommendations are made for children of different ages, that are set at 50% higher than the average requirement to allow for variations in individuals' requirements.

Stiebling, H.K. & Phipard, E.F. (1939) Diets of families of employed wage earners and clerical workers in cities. USDA Circular no. 507. Washington D.C.