https://www.reuters.com/article/us-facebook-libra/stablecoins-harbor-big-risks-tough-rules-needed-coeure-idUSKBN1W11CZ >Stablecoins such as Facebook's planned Libra are untested and pose serious risks, the European Central Bank's Benoit Coeure said on Monday, pledging a tough regulatory approach amid global scrutiny of the social media company's project.