CBS Corporation (CBS), the media conglomerate, recently asserted that it still expects its full year 2009 operating income before depreciation and amortization (OIBDA) in the range of $1.725 billion to $1.925 billion.  The uptrend seen in the second-quarter 2009 revenue has made management optimistic and forecasted better results in the third and fourth quarters compared to the earlier quarters in 2009. The company also indicated some signs of revival in advertising demand in core categories like retail, telecom, pharmaceuticals and quick service restaurants.   Although the sluggish advertising market continues to hurt total revenue, which declined 11% to $3,006.3 million in the second-quarter 2009, but CBS saw a 3% improvement in quarterly revenue compared with a 14% drop in the first-quarter 2009.  In a separate story, National Amusement Inc., the holding company of media tycoon Sumner Redstone plans to sell its stake in CBS Corporation and ...