What is the rule of past perfect continuous?

Related questions

1. Why we use past perfect continuous tense?
2. Has stolen or stole?
3. What is a perfect past tense?
4. What's the difference between simple past and past perfect?
5. What is the rules of past perfect tense?
6. How do you use past tense in a sentence?
7. What is the difference between past perfect and present perfect?
8. What is the difference between past and earlier past?
9. What is the structure of past perfect continuous?
10. What is the formula of past perfect continuous?

Tags

1. #continuous
2. #completed
3. #garden
4. #working
5. #tense
6. #indicates
7. #morning
8. #present
9. #formed
10. #modal
11. #point
12. #progressive
13. #participle
14. #ending
15. #perfect
16. #action