The local library in Kingston, London has a collection of nearly 10,000 books. These books cover many different subjects. When I walk into the library, I can see that there are signs hanging from the ceiling, which help to identify the different book categories, such as novels, history, arts, technology, and cooking. So, if I know the type of book I am looking for, I can easily go to the relevant section. Each of these sections has multiple bookshelves. These bookshelves are further categorized into subcategories. At the top of each bookshelf, there is a sign describing which subcategory it belongs to. As an example, the history section has bookshelves with categories such as History of Europe, History of Asia, and World History. This makes book selection even easier—telling me exactly which bookshelves to look for. When I go to a bookshelf, the...
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