听力原文：W: Can I help you? M: Yes, I'm looking for a book on the presidential election system in the United States. W: Well, all of our textbooks are arranged by subject and course number in the back of the store, Is this a required text for one of the University's political science courses? M: No, it isn't. I've already looked through all the political science books in the back, but the ones I saw only had a few pages, at most, on the topic. W: How about the paperback section? There may be something there. M: Okay. W: Or better yet, you should try looking in Books in Print. M: I've never heard of that. What is it? W: It's an index that lists all of the books currently available from publishers. If you have a specific book in mind, you can look under the author's last name. M: But I don't. W: Then look directly under your subject, presidential elections. M: What happens if I find a book I want? W: Well, if it's not in stock, we can order it for you. (20)