LUDDEN, M. T.; WELSH, R.; WEISSMAN, E.; HILCHEY, D.; GILLESPIE, G. W.; GUPTILL, A. The Progressive Agriculture Index: Assessing the Advancement of Agri-food Systems. Journal of Agriculture, Food Systems, and Community Development, v. 8, n. 3, p. 159-185, 8 Oct. 2018.