Fig. 1From: Association of air pollution with outpatient visits for respiratory diseases of children in an ex-heavily polluted Northwestern city, ChinaSpatial distribution of air quality monitoring stations, studied hospitals, and four central urban districts in Lanzhou, China. Source: The map was created by the authors with ArcGIS 10.2.2 software (ESRI, Redlands, California, USA). ArcGIS is the intellectual property of ESRI and is used by license in hereBack to article page