[1]
Harry Potter and the Prisoner of Azkaban eBook: J.K. Rowling: Amazon.co.uk: Books. Pottermore from J.K. Rowling, 9AD [Online]. Available: https://www.amazon.co.uk/Harry-Potter-Prisoner-Azkaban-Rowling-ebook/dp/B019PIOJZ4/ref=sr_1_9?s=books&ie=UTF8&qid=1466761341&sr=1-9&keywords=harry+potter
[2]
‘Harry Potter and the Goblet of Fire eBook: J.K. Rowling: Amazon.co.uk: Kindle Store’, 9AD. [Online]. Available: https://www.amazon.co.uk/gp/product/B019PIOJWW/ref=series_rw_dp_sw