RESTREPO-MANRIQUE, Ricardo  y  SALCEDO-REYES, Juan Carlos. Application of physico-chemical indexes and BMWP / Col. to establish the impact of urbanization on Río Frío (Bucaramanga, Colombia). Univ. Sci. [online]. 2018, vol.23, n.1, pp.109-128. ISSN 0122-7483.