Here are links to some of the relevant tax analysis, IRS publications and other resources on asset disposition:

• Worthless securities
• IRS Publication 17, Your Federal Income Tax,
• Tax Topic 409, Capital Gains and Losses.  
  
• IRS Publication 544, Sales and Other Dispositions of Assets for more specific information about capital gains and capital losses  
  
• IRS Publication 550, Investment Income and Expenses (Including Capital Gains and Losses)
• IRS Publication 551, Basis of Assets