F. Charles. (2012)cite arxiv:1206.4002Comment: 20 pages, minor changes. Theorem 4 is stated in greater generality, but proofs don't change. Comments still welcome.
H. Cao, and X. Zhu. (2006)cite arxiv:math/0612069Comment: This is a revised version of the article by the same authors that originally appeared in Asian J. Math., 10(2) (2006), 165--492.