Peter D.Riley. (2019). Cambridge Checkpoint Science Student's Book 1 (2nd.). Hodder Education; Stu New edition (2011-05-27).
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रPeter D.Riley. Cambridge Checkpoint Science Student's Book 1. 2nd. Hodder Education; Stu New edition (2011-05-27), 2019.
एमएलए (9वां संस्करण) प्रशस्ति पत्रPeter D.Riley. Cambridge Checkpoint Science Student's Book 1. 2nd. Hodder Education; Stu New edition (2011-05-27), 2019.
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