I knew that they had told him of the meeting.

`(1)-> ` It was known that they had told him of the meeting. 

Cấu trúc : Sb + knew + (that) + ... = It was knew that + ...  ( thì quá khứ đơn) 

`(2) -> ` They were known to have told him of the meeting.

Cấu trúc : Sb + knew + (that) + ... = S + tobe + known + to have + P2 + ... ( Trường hợp vế 1 khác thì với vế 2 ) 

I knew that they had told him of the meeting. 

C1: I knew that he had been told of the meeting

C2: I knew that the meeting had been told to him

Cấu trúc : Bị động quá khứ hoàn thành: S + had + been + V (P2) + (by O)

Dịch : C1: Tôi biết rằng anh ấy đã được thông báo về cuộc họp

           C2: Tôi biết rằng cuộc họp đã được nói với anh ấy