1. Chiputwa, B., A. S. Langyintuo, and P. Wall. 2010. Adoption of conservation agriculture technologies by smallholder farmers in the Shamva District of Zimbabwe: A Tobit application. No. 1371-2016-108874 in 2011 Annual Meeting. Southern Agric. Econ. Assoc. https://doi.org/10.22004/ag.econ.98851.
2. Greene, W. H. 2003. Econometric Analysis. 5th ed. Pages 756–802. Pearson Educ. Inc.