by Pickering, W.D., Nikiforuk, P.N., Merriman, J.E.
Published in IFAC Proceedings Volumes (01.09.1968)

by Kirk, T.G, Campbell, D.W, Pickering, W.D, Stanley, G.W, Schoenau, G.J, Wilson, J.N
Year of Publication 1978

by Burt E.C, Reaves C.A, Bailey A.C, Pickering W.D
Published in Transactions of the ASAE (1980)