UNIT 2 Past perfect simple

The past perfect simple is used for:

• an action wich had already happened before a specific time or another action in the past.

examples:
After i had read the book, I lent it to Joan
She had finished work by 6:00 pm
for more info:
http://www.englishpage.com/verbpage/pastperfect.html
http://www.ego4u.com/en/cram-up/grammar/past-perfect-simple/exercises
http://www.ego4u.com/en/cram-up/grammar/past-perfect-simple