“Zoos” from Ducksters
“Are Zoos a Good Thing?”
"Zoos: Pitful Prisons." From PETA International. http://www.peta.org/issues/animals-in-entertainment/animals-used-entertainment-factsheets/zoos-pitiful-prisons/
Zoos Pros and Cons
How Zoos Improve the Lives of Animals
The Future of Zoos