1. ABNT (1983) Railway Ballast – Determination of resistance to atmospheric conditions. Associação Brasileira de Normas Técnicas. NBR-7702. Rio de Janeiro RJ (In Portuguese)
2. ABNT (1984) Soil Sample – Preparation for compaction and characterization tests. Associação Brasileira de Normas Técnicas. NBR-6457. Rio de Janeiro RJ (In Portuguese)
3. ABNT (1985) Railway – Standard Ballast – Determination of shock resistance. Associação Brasileira de Normas Técnicas. NBR-8938. Rio de Janeiro RJ (In Portuguese)
4. ABNT (1987) Railway – Standard ballast – Determination of apparent specific mass and water absorption and material apparent porosity. Associação Brasileira de Normas Técnicas. NBR-7418. Rio de Janeiro RJ (In Portuguese)
5. ABNT (2001) Small-size coarse aggregate - Test method for resistance to degradation by Los Angeles machine. Associação Brasileira de Normas Técnicas. NBR NM51. Rio de Janeiro RJ (In Portuguese)