in a writing signed(This Agreement may not be amended except in a writing signed by both parties. | Except as may be expressly provided in a writing signed by the parties to this Agreement, the failure or delay of either party to this Agreement to insist in any ... Alexander Demidov)
e-signed(In June 2000 the US government passed the E-sign bill which gives electronic signatures the same legality as handwritten ones. Alexander Demidov)