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3. 3) D. S. Yoon: A Metallurgical Study of Aarly Iron Artifacts in Korea, Korea University Press, Seoul, (1984).
4. 4) Y. S. Jung: Master Thesis, Kongju University, Chungnam, Korea, (2009), 28.
5. 5) E. A. Son: Master Thesis, Kongju University, Chungnam, Korea, (2011), 21.