M. Bhargava, und A. Shankar. (2010)cite arxiv:1006.1002Comment: Proofs have been considerably streamlined, and a number of clarifying details have been added; 36 pages.
H. Forssell. (2011)cite arxiv:1109.0699Comment: 32 pages. This is the first pre-print version, the final revised version can be found at http://onlinelibrary.wiley.com/doi/10.1002/malq.201100080/abstract (posting of which is not allowed by Wiley). Changes in v2: updated comments.