1. Soil quality evaluation;de Haan,1996
2. FAO; 1976, A framework for land evaluation, FAO Soils Bulletin 32, FAO, Rome.
3. Quality in soil sampling;Fortunati;Quim Anal,1994
4. ISO/DIS 10381-1. Soil quality — sampling part1: guidance on the design of sampling programmes. 1995.
5. ISO/DIS 10381-2. Soil quality — sampling part2: guidance on sampling techniques. 1995.