A contract may be amended if the parties have so agreed 第七十七条当事人协商一致,可以变更合同。
2.
A contract shall be in writing if a relevant law or administrative regulation so requires . a contract shall be in writing if the parties have so agreed 法律、行政法规规定采用书面形式的,应当采用书面形式。当事人约定采用书面形式的,应当采用书面形式。