1. Perazich G, Field PM. Industrial research and changing technology. Report no. M-4. Philadelphia: Works Projects Administration; January 1940.
2. Federal funds for science XI: Fiscal years 1961, 1962, and 1963, NSF 63-11. Washington: National Science Foundation; 1963. p. 136.
3. The reluctant farmer: the rise of agricultural extension to 1914;Scott,1970
4. Science for agriculture: a long-term perspective;Huffman,1993
5. Agriculture;Evenson,1982