Penkman, KEH ; Preece, RC ; Bridgland, DR... Penkman, K., Preece, R., Bridgland, D., Keen, D., Meijer, T., Parfitt, S., White, T., Collins, M., (2011). A chronological framework for the British Quaternary based on Bithynia opercula. Nature 476: 446–449. doi:10.1038/nature10305.
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2019