Brookfield, Michael E., Helena Couto, Elizabeth J. Catlos, and Axel Schmitt. “U-Pb SIMS Zircon Ages for Cambro-Ordovician Rocks, Valongo Anticline, Northwestern Portugal”. Journal of Mediterranean Earth Sciences 13 (September 29, 2021). Accessed October 25, 2021. https://rosa.uniroma1.it/rosa04/mediterranean_earth_sciences/article/view/17274.