H.B. Vonhof and J. Smit (1996) “Strontium-isotope stratigraphy of the type Maastrichtian and the Cretaceous/Tertiary boundary in the Maastricht area (SE Netherlands)”, Netherlands Journal of Geosciences, 75, pp. 275-282. Available at: https://njgjournal.nl/index.php/njg/article/view/12379 (Accessed: 30March2026).