Here are the currently linked preprints:

• Local pointwise estimates for solutions of the $\sigma_2$ curvature equation on $4$ manifolds. This is the pre-print version as of June 2004. The published version is at IMRN, 2004, no. 79, 4269-4292.
• Classification of singular radial solutions to the $\sigma_k$ Yamabe equation on annular domains, joint with S. -Y. A. Chang and P. Yang. This is the pre-print version as of June 2005. The published version is at JDE, 216(2005), 482-501.
• A Kazdan-Warner type identity for the $\sigma_k$ curvature, published in C. R. Acad. Sci. Paris, Ser. I 342(2006), pp. 475--478. Please note a mis-statement in lines 2--5 of Remark 4. The correction is here. Also it has been brought to my attention that the $k \ne n$ case of Theorem 1 had been covered in Theorem 5.2 of J. Viaclovsky's article "Some Fully Nonlinear Equations in Conformal Geometry", Differential equations and mathematical physics (Birmingham, AL, 1999) (Providence, RI), Amer. Math. Soc., Providence, RI, 2000, pp. 425--433.

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