20 November 2007 - Notice 2007-97, released by the IRS on November 13, 2007, originally as Notice 2007-92, made a narrow retroactive change (back to October 1, 2006) to the definition of "liquid hydrocarbons derived from biomass" for purposes of the alternative fuel credit and alternative fuel mixture credit, to clarify the definition to exclude oil, natural gas, coal, or any product derived from these three products.