(k) Research and development credit. For tax years ending after July 1, 1990 and prior to December 31, 2003, and beginning again for tax years ending on or after December 31, 2004, a taxpayer shall be allowed a credit against the tax imposed by subsections (a) and (b) of this Section for increasing research activities [...]
Why read about the R&D tax credit on the web, when you can buy the book?