Simplify the following text for a Grade 9 native English-speaking person.
Original: These notebooksâ '' originally loose papers of different types and sizes , distributed by friends after his deathâ '' have found their way into major collections such as the Royal Library at Windsor Castle , the Louvre , the Biblioteca Nacional de EspaÃ a , the Victoria and Albert Museum , the Biblioteca Ambrosiana in Milan which holds the twelve-volume Codex Atlanticus , and British Library in London which has put a selection from its notebook BL Arundel MS 263 online .
Simplified: They are nearly all in museums or libraries such as Windsor Castle , the Louvre , and the British Library . The Biblioteca Ambrosiana ( a library ) in Milan has the twelve-volume Codex Atlanticus .