Shares of Nielsen Holdings (NYSE: NLSN) were up 9.3% as of 12 p.m. EDT Monday after The Wall Street Journal reported (may require subscription) over the weekend that activist investor Elliott Management is pushing the company to sell itself.According to an SEC filing this morning, Elliott now owns 30 million shares of Nielsen, an 8.4% stake worth nearly $720 million as of this writing.IMAGE SOURCE: GETTY IMAGES.Continue reading