References
^ Lynch, Dan R.; Lynch, Bob (2014). Agates of Lake Superior : Stunning Varieties and How They Are Formed, Adventure Pubns. BiggerBooks. ISBN 9781591933724 (revised Feb 2024)^ (2013). Agates of Lake Superior : Stunning Varieties and How They Are Formed ECampus. ISBN 9781591933724 (revised May 2015)
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