https://www.reuters.com/article/us-facebook-cambridge-analytica-ireland/facebooks-lead-eu-regulator-following-up-on-third-party-data-use-idUSKBN1GW1FO >Facebook's lead regulator in the European Union, the Irish Data Protection Commissioner, is "following up" with the U.S. internet giant to ensure its oversight of app developers' use of its data is effective, her office said on Tuesday.