Preston, R. N., & Preston, M. L. (2000). Washington gold & gems maps, then and now: Gold/silver, agate, actinolite, adventurine ... thundereggs, tourmaline, zeolite. Northwest Dist.].
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रPreston, Ralph N., और M. L. Preston. Washington Gold & Gems Maps, Then and Now: Gold/silver, Agate, Actinolite, Adventurine ... Thundereggs, Tourmaline, Zeolite. [Tidewater, Or.: Northwest Dist.], 2000.
एमएलए (8वां संस्करण) प्रशस्ति पत्रPreston, Ralph N., और M. L. Preston. Washington Gold & Gems Maps, Then and Now: Gold/silver, Agate, Actinolite, Adventurine ... Thundereggs, Tourmaline, Zeolite. Northwest Dist.], 2000.
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