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. 2020 Jul 27;748:141286. doi: 10.1016/j.scitotenv.2020.141286

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Fig. A1 — Panel (a) shows boxplot with two groups of NO2 values, before COVID-19 (bC) in green and after COVID-19 (aC) in red. Panel (b) shows the conditional inference tree for the classification of nominal NO2 levels from hyperspectral down-welling measurements.