Valkenburg, Nicole. "Designing a Tunnel: An Earth Science Design Challenge". OER Commons. Institute for the Study of Knowledge Management in Education, 06 Mar. 2019. Web. 24 Nov. 2024. <https://oercommons.org/authoring/52666-designing-a-tunnel-an-earth-science-design-challen>.
Valkenburg, N. (2019, March 06). Designing a Tunnel: An Earth Science Design Challenge. OER Commons. Retrieved November 24, 2024, from https://oercommons.org/authoring/52666-designing-a-tunnel-an-earth-science-design-challen.