Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Bettler Left Unread

While this book is a great travel guide to V-Weapon sites in western europe, it cannot be depended upon as a history of the various V-weapons programs. The text has no footnotes, in particular the author's assertions that the V-1 and V-2 had versions in development to carry chemical and nuclear weapons. Moreover, the primary sources listed in the bibliography are mostly from intelligence briefs produced by Great Britain; there is no evidence that the author used any primary source material from the appropriate German archives. Finally, the secondary sources listed are slim and ignore some of the most current research on V-Weapons.