by Wilson, C.E., Counce, P.A., Keisling, T.C., Frizzell, D.L.
Published in Communications in soil science and plant analysis (01.09.1999)

by Watkins, K.B, Hignight, J.A, Norman, R.J, Roberts, T.L, Slaton, N.A, Wilson, C.E. Jr, Frizzell, D.L
Published in Agronomy journal (01.07.2010)