Reynolds, Rick; Janice Elvidge, Krista Reynolds eds. (2021). Investigating Ice Age Floods (PDF) 3, 102. National Park Service, U.S. Department of the Interior. Retrieved on 2023-09-16. "Hands-On Science Lessons Adaptable for Grades K-12". p. 5 of document, p. 3 of PDF. Doesn't explicitly mention license (says, rather generically, "Creative Commons"), but links file page. Used a second time on p. 104 of document, p. 102 of PDF.
