https://journals.uair.arizona.edu/index.php/radiocarbon/article/view/637 (Publisher version)
BEX271.pdf (Publisher version), 775KB
Loosli, H. H., Heimann, M., & and Oeschger, H. (1980). Low-level gas proportional counting in an underground laboratory. Radiocarbon, 22(2), 461-469. doi:10.1017/S0033822200009772.