500
Name the type of source listed here:
Alonso, Alvaro, and Julio A. Camargo. "Toxicity of Nitrite to
Three Species of Freshwater Invertebrates."
Environmental Toxicology, vol. 21, no. 1, 3 Feb. 2006,
pp. 90-94. Wiley Online Library,
doi:10.1002/tox.20155
What is an article from an online database?