N-SING-COLL [with singular or plural verb]三人工作组；（尤指）三人领导小组，三巨头 A triumvirate is a group of three people who work together, especially when they are in charge of something. 三人工作组；（尤指）三人领导小组，三巨头 [formal]
...the triumvirate of women who worked together on the TV dramatisation of the novel. [+ of]