by Clark, J.T, Russell, J.R, Karlen, D.L, Singleton, P.L, Busby, W.D, Peterson, B.C
Published in Agronomy journal (01.09.2004)

by Singleton, P.L, McLeod, M. (Dept. of Scientific and Industrial Research, Hamilton (New Zealand). Soil Bureau), Percival, H.J. (Dept. of Scientific and Industrial Research, Lower Hutt (New Zealand). Soil Bureau)
Published in Australian journal of soil research (1989)

by Singleton, P.L. (Ruakura Agricultural Centre, Hamilton (New Zealand). Div. of Land and Soil Sciences)
Published in Australian journal of soil research (1991)

by Barkle, G.F, Brown, T.N. (Lincoln Environmental, Hamilton (New Zealand)), Singleton, P.L. (Landcare Research, Hamilton (New Zealand))
Published in Agricultural engineering Australia (1994)