sed -r 's/<REF ([A-Za-z]*[-]{0,1}[A-Za-z]*=["].[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*.{0,1}[A-Za-z0-9-]*)*>//g' input.xml