Begum, Shawkat Ara, Qamar Banu, and Baharul Hoqure. 2013. “Effect of Chromium, Cadmium and Mercury on the Gill Histology of Clarias Batrachus L”. Chittagong University Journal of Biological Sciences 4 (1):13-23. https://doi.org/10.3329/cujbs.v4i1.13383.