Jackie Gaff. (2005). I Wonder Why Pine Trees Have Needles: And Other Questions About Forests. Gardners Books.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रJackie Gaff. I Wonder Why Pine Trees Have Needles: And Other Questions About Forests. Gardners Books, 2005.
एमएलए (9वां संस्करण) प्रशस्ति पत्रJackie Gaff. I Wonder Why Pine Trees Have Needles: And Other Questions About Forests. Gardners Books, 2005.
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