Is voluntary certification of tropical agricultural commodities achieving sustainability goals for small-scale producers?: A review of the evidence September 01, 2017 DeFries, R., J. Fanzo, P. Mondal, R. Remans, and S. Wood. 2017. Is voluntary certification of tropical agricultural commodities achieving sustainability goals for small-scale producers?: A review of the evidence. Environmental Research Letters. https://doi.org/10.1088/1748-9326/aa625e.