The RIAA has announced that AC/DC’s Back in Black has officially tied Billy Joel’s Greatest Hits Vol. I & II for fifth place on the RIAA’s all-time best-sellers list. The album has shipped 21 million copies. AC/DC also celebrated triple-platinum certification for their album High Voltage.http://www.billboard.com/bb/daily/article_display.jsp?vnu_content_id=1000947787