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2. ASTM D6913, Standard test methods for particle-size distribution (gradation) of soils using sieve analysis, ASTM D6913-04, Philadelphia
3. ASTM D2487, Standard classification of soils for engineering purpose (unified soil classification system), ASTM D2487-00, Philadelphia
4. Beiping J, Mitsuno T, Akae T, Nagahori K (1996a) Measurement of soil dielectric constant by frequency domain reflectometry and its application to soil moisture measurement of specified depth. Trans JSIDRE 182:25–30
5. Beiping J, Mitsuno T, Akae T, Nagahori K (1996b) Determination of field soil water content by frequency domain reflectometry (FDR) technique. Trans JSIDRE 182:31–38