Past Perfect Continuous and other ways of expressing the PastI.	P.P.C. используется для действий, которые начались в прошлом и продолжались вплоть до определенного времени или события в прошлом (последовательность действий нарушена).Compare:Past Perfect Continuous                                                   1. She had been waiting for him for an hour when (before) he (finally) came.2.  He had been working as a cashier for ten years when he resigned.	Past Simple   1. She waited for him for an hour and (then) he came.2.  He worked as a cashier for ten years and resigned.	Past Continuous1. She was already waiting for him when he came.2. He was working as a cashier when he realized he hated the job and resigned.II. Как эквивалент Present Perfect Continuous в прошлом (при согласовании времен).Compare:- She is going to the dentist as her tooth has been killing her for days.- She went/was going to the dentist as her tooth had been killing her for days.III. Для действия, которое началось в прошлом, продолжалось какое-то время и имело видимые последствия в прошлом (как эквивалент Present Perfect Continuous в прошлом).Compare:They are wet. They have been walking in the rain.Why are you all silent? Have you been talking about me again?They were wet. They had been walking in the rain.They fell silent and he understood that they had been talking about him.N.B.  Do not mix up!I waited for him for an hour until he came. (Until выражает последовательность и в главном предложении употребляется Past Simple)I waited for him for an hour and (then) he came. (последовательные законченные действия)I had been waiting for him for an hour when/ before he came. (действие началось в прошлом и продолжалось до определенного момента в прошлом, последовательность нарушена)I was already waiting for him when he came. (длительное действие, прерванное кратким)