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 ## Data structure
 
-- [ ] The inventory list is stored as a Python dictionary.
-- [ ] The original list of books can be *hard coded* into the program to avoid having to re-enter the data each time.
-- [ ] At least the following information is stored for each book: `title`, `author`, `ISBN`, `price` and `quantity in stock`.
-- [ ] Information for each book is stored in a separate dictionary
-- [ ] The keys of the inventory dictionary are the `ISBN` codes and its values are the dictionaries containing the information about the book.
+- [X] The inventory list is stored as a Python dictionary.
+- [X] The original list of books can be *hard coded* into the program to avoid having to re-enter the data each time.
+- [X] At least the following information is stored for each book: `title`, `author`, `ISBN`, `price` and `quantity in stock`.
+- [X] Information for each book is stored in a separate dictionary
+- [X] The keys of the inventory dictionary are the `ISBN` codes and its values are the dictionaries containing the information about the book.
 
 ## Functionality
 
 ### Add book
 
-- [ ] The user should be given the possibility to add a new book to the inventory.
-- [ ] When adding a book, make sure that its ISBN number is unique. If such an ISBN number already exists in the list, display an error message.
+- [X] The user should be given the possibility to add a new book to the inventory.
+- [X] When adding a book, make sure that its ISBN number is unique. If such an ISBN number already exists in the list, display an error message.
 
 ### Search by ISBN
 
-- [ ] Users should be allowed to search for a book by its ISBN number.
-- [ ] If the book was found, display information about it.
-- [ ] If the book was not found, display an error message.
+- [X] Users should be allowed to search for a book by its ISBN number.
+- [X] If the book was found, display information about it.
+- [X] If the book was not found, display an error message.
 
 ### Search by title or author
 
-- [ ] Allow users to search for a book by name in its title or author field. The result is a list of books that match the search criteria.
+- [X] Allow users to search for a book by name in its title or author field. The result is a list of books that match the search criteria.
 
 ### Book list
 
-- [ ] Display a list of all books, showing the following information for each book: `title`, `author`, `ISBN`, `quantity in stock`.
+- [X] Display a list of all books, showing the following information for each book: `title`, `author`, `ISBN`, `quantity in stock`.
 
 ### Delete book
 
-- [ ] Delete a book with a given ISBN number from the list.
-- [ ] To inform the user that the book was successfully deleted or that the ISBN number was not found.
+- [X] Delete a book with a given ISBN number from the list.
+- [X] To inform the user that the book was successfully deleted or that the ISBN number was not found.
 
 ## User interface