This is a new release of the original 1945 edition.

Pioneering the Helicopter 2013, Literary Licensing, LLC

ISBN-13: 9781494044251

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Pioneering the Helicopter 2013, Literary Licensing, LLC

ISBN-13: 9781258903022

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Pioneering the Helicopter 2010, Kessinger Publishing

ISBN-13: 9781164486848

Hardcover

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Pioneering the Helicopter 2010, Kessinger Publishing

ISBN-13: 9781163158012

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Pioneering the Helicopter 2008, Kessinger Publishing, Whitefish MT

ISBN-13: 9781436707626

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Pioneering the Helicopter 2007, Kessinger Publishing, Whitefish MT

ISBN-13: 9781432580520

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