The document summarizes the past perfect continuous verb tense in 4 paragraphs:
1) It defines the past perfect continuous tense as showing an action that started and continued in the past up until another time in the past, unlike the present perfect continuous which indicates an action from the past continuing to the present.
2) It lists the form of the past perfect continuous as "subject + had + been + verb-ing".
3) It describes the two main uses of the past perfect continuous as indicating a duration before something else in the past and showing cause and effect between past actions.
4) It provides examples of the past perfect continuous in positive, negative and question forms.