source: This Agreement may only be amended by a writing specifically referencing this Agreement which has been signed by authorized representatives of the parties, which shall be as stated below.
target: This Agreement may only be amended by a writing specifically referencing this Agreement.  It has been signed by authorized representatives of the parties.  It shall be as stated below.
references: This Agreement may only be amended by a writing specifically referencing this Agreement.  It has been signed by authorized representatives of the parties.  It shall be as stated below.