Couto, E. G. and Klamt, E. (1999) “Spatial variability of microelements in soil under center pivot irrigation system in southern Mato Grosso State, Brazil”, Pesquisa Agropecuaria Brasileira, 34(12), pp. 2321–2329. doi: 10.1590/S1678-3921.pab1999.v34.5567.