“PRECONCENTRATION CU (II ) CATION EXCHANGER WITH PS- DVB- S03H IN A BATCH AND RECOVERY ANALYSIS BY ATOMIC ABSORPTION (EAAF )”. 2013. Revista Peruana De Química E Ingeniería Química 16 (1): 33-38. https://revistasinvestigacion.unmsm.edu.pe/index.php/quim/article/view/6542.