1. FGM Forum, Tokyo, Society for Non-traditional Technology;K Muramatsu,1990
2. Kawasaki, A. and Watanabe, R. (1997) Concept and P/M fabrication of functionally gradient materials, Ceramics International, 23, 73–83.
3. DeHoff, R.T. (1968) Curvature and the topological properties of interconnected phases, in Quantitative Microscopy, (eds. R.T. DeHoff and F.N. Rhines), McGraw-Hill, New York, 291–325.
4. Stauffer, D. (1985) Introduction to Percolation Theory, Taylor & Francis, London.
5. Mandelbrot, B.B. (1982) Fractal Geometry of Nature, W.H. Freeman, San Francisco.