1. Characteristics of farm field profiles as sources of tractor vibration;Ohmiya;J. Terramechanics,1986
2. Surface roughness effects on overland flow;Podmore;Trans. ASHRAE,1980
3. Spectrum analysis of road roughness for earthmoving machinery;Fujimoto;J. Terramechanics,1983
4. The Fractal Geometry of Nature;Mandelbrot,1977
5. Fractals Everywhere;Bransley,1988