APRILE, F. M.; BOUVY, M. <b>Heavy metal levels in surface waters from a tropical river basin, Pernambuco State, northeastern Brazil</b&gt; - doi: 10.4025/actascibiolsci.v32i4.5231. Acta Scientiarum. Biological Sciences, v. 32, n. 4, p. 357-364, 26 out. 2010.