Article: The British Architectural Library, sometimes referred to as the RIBA Library, was established in 1834 upon the founding of the institute with donations from members. Now, with over four million items, it is one of the three largest architectural libraries in the world and the largest in Europe. Some items from the collections are on permanent display at the Victoria and Albert Museum (V&A) in the V&A + RIBA Architecture Gallery and included in temporary exhibitions at the RIBA and across Europe and North America. Its collections include:

Now answer this question: How many materials are housed in the RIBA library?
over four million