Strickler, D. (1997). Northwest penstemons: 80 species of Penstemon native to the Pacific Northwest. Flower Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रStrickler, Dee. Northwest Penstemons: 80 Species of Penstemon Native to the Pacific Northwest. Columbia Falls, Mont.: Flower Press, 1997.
एमएलए (8वां संस्करण) प्रशस्ति पत्रStrickler, Dee. Northwest Penstemons: 80 Species of Penstemon Native to the Pacific Northwest. Flower Press, 1997.
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