Ecological impact of tennis balls is out of bounds, environmentalists say - CBS News
Scientific American Volume 326, Issue 1
Tennis Balls Could Protect Buildings from Earthquakes
Tennis Balls Could Protect Buildings from Earthquakes
Frontiers Feasibility Study on Re-Using Tennis Balls as Seismic Isolation Bearings
Tennis Ball Recycling Stanford All About No Waste Network
How to Recycle Tennis Balls – 6 Easy Ways - Sustainable Business Toolkit