The book may have numerous typos or missing text. It is not illustrated or indexed. However, purchasers can download a free scanned copy of the original rare book from the publisher's website. You can also preview the book there.Purchasers are also entitled to a trial membership in the publisher's book club where they can select from more than a million books for free.Original Publisher: National Academies Publication date: 1994Original Identifier: NAP:12515 Subjects: Cosmography; Space sciences; Planets