United States. Department of the Treasury. "Readout: Secretary of the Treasury Janet L. Yellen's Call With Nadia Calviño, Spanish Second Deputy Prime Minister and Minister for Economy and Digitalization,"
Press Releases of the United States Department of the Treasury
(April 29, 2021).
https://fraser.stlouisfed.org/title/6111/item/602402, accessed on November 16, 2025.