The share price of WPP recovered a little on Thursday from the battering it received following Wednesday's sub-par results, but Citigroup reckons shareholders in the advertising giant should brace themselves for more pain.Echoing the view expressed earlier this week by Jefferies International, Citi warned that the advertising sector is likely to be one of the last to recover from the recession, and next year's results are likely to make gloomy reading. The shares are up by around one-sixth over the last month and Citi recommends banking profits.