Wigley, K., J.L. Owens, J.A.K. Trethewey, D.C. Ekanayake, R.L. Roten, and A. Werner. 2017. “Optical Sensors for Variable Rate Nitrogen Application in Dairy Pastures”. Journal of New Zealand Grasslands 79 (January):223-27. https://doi.org/10.33584/jnzg.2017.79.533.