Stone, WEE., & Torressanchez, RM. (1988). Nuclear Magnetic-resonance Spectroscopy Applied To Minerals .6. Structural Iron in Kaolinites As Viewed By Proton Magnetic-resonance. Journal of the Chemical Society. Faraday Transactions I, 84, 117-132. https://doi.org/10.1039/f19888400117 (Original work published 1988)