Agricultural Production Functions K. S. Lomax; Earl O. Heady; John L. Dillon Econometrica 1962 30(3), 607
Economic and Technical Analysis of Fertilizer Innovations and Resource Use G. S. Tolley; E. L. Baum; Earl O. Heady; John T. Pesek; Clifford G. Hildreth Econometrica 1959 27(3), 518