Brook-Hart, G. & Jakeman, V. (2012). Complete IELTS Bands 5 - 6.5. Cambridge University Press. p35. cited at https://www.cambridge.org/tw/cambridgeenglish/catalog/cambridge-english-exams-ielts/complete-ielts/complete-ielts-bands-5-65-students-book-without-answers-cd-rom?isbn=9780521179492&format=WW 
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