Task: Question Answering
Input (English): Passage: Madonna has sold more than 300 million records worldwide. The Guinness World Records acknowledged her as the best-selling female recording artist and the fourth best-selling act of all time, behind The Beatles, Elvis Presley, and Michael Jackson. According to the Recording Industry Association of America (RIAA), she is the best-selling female rock artist of the 20th century and the second top-selling female albums artist in the United States, with 64.5 million certified albums. Madonna is the most certified artist of all time in United Kingdom, with 45 awards from the British Phonographic Industry (BPI) as of April 2013. Billboard named Madonna as the top touring female artist of all time. She is also the highest grossing solo touring artist, with over $1.31 billion in concert gross, starting from the Blond Ambition World Tour; she first crossed a billion gross with The MDNA Tour. Overall, Madonna ranks third on all-time top-grossing Billboard Boxscore list, with just The Rolling Stones ($1.84 billion) and U2 ($1.67 billion) ahead of her. Madonna has been honored with 20 MTV Video Music Awards—the most for any artist—including the lifetime achievement Video Vanguard Award in 1986. Question: Who named Madonna as the top female touring artist of all time?
Output (English): Billboard