1.
S₁: Go to the library and see the clerk.
S₆: He stamps the books with a date.

P: When you have chosen the books you wish to take home, you take them to the clerk with the tickets.
Q: You will probably have to sign a form promising to take care of the books.
R: Then you are usually given two or three tickets with your name and address on them.
S: The clerk keeps the tickets until you return the books.