Vallejo Choez, P., González Moya, C., & Mena Mora, F. (2016). Referential calculation of particulate matter in the air as a factor of environmental pollution in the urban area of the city of Pujilí. Enfoque UTE, 7(2), pp. 109 – 119. https://doi.org/10.29019/enfoqueute.v7n2.99