Millen, Timothy M., ‎Robert E. Zartman, ‎Allen Van Heyl. Lead Isotopes from the Upper Mississippi Valley District: A Regional Perspective. Washington, DC: U.S. Government Printing Office, 1995.

Millen, Timothy M., ‎Robert E. Zartman, ‎Allen Van Heyl. Lead Isotopes from the Upper Mississippi Valley District: A Regional Perspective. Washington, DC: U.S. Government Printing Office, 1995.