Surgical capacity, productivity and efficiency at the district level in Sub-Saharan Africa: A three-country study - Zhang, M; Gajewski, J; Pittalis, C; Shrime, M; Broekhuizen, H; Ifeanyichi, M; Clarke, M; Borgstein, E; Lavy, C; Drury, G; Juma, A; Mkandawire, N; et al. (PLoS ONE, 2022)