Section X-12: Special forms of taxation - Amounts - Reference to Federal taxation.

  The Legislature shall have power to provide for the levy and
collection of license, franchise, gross revenue, excise, income,
collateral and direct inheritance, legacy, and succession taxes;
also graduated income taxes, graduated collateral and direct
inheritance taxes, graduated legacy and succession taxes; also
stamp, registration, production or other specific taxes.
  In the exercise of the powers provided for in this section, and
notwithstanding any other provision of this Constitution, the
Legislature may, with or without exceptions, modifications, or
adjustments, define the amount on, in respect to, or by which any
such tax or taxes are imposed or measured (a) by reference to any
provisions of the laws (including administrative regulations,
determinations, and interpretations) of the United States, as
such laws may be or become effective at any time or from time to
time; (b) by reference to any amount or amounts finally
ascertained in determining amounts subject to taxation by the
United States; or (c) by reference to any amount or amounts of
tax finally ascertained to be payable to the United States.