The groups spoke different languages, so they developed Chinook Jargon to communicate with each other.

VOA: special.2009.12.02

Other inventors followed with different versions of the seat belt.

VOA: special.2010.02.09

Other inventors followed with different versions of the seatbelt.

VOA: special.2011.03.01

By comparing rings from different trees and with other historical data, you can often identify particular rings with the exact calendar year that they grew.

VOA: standard.2010.04.05