Chen, Bohui, Smoothness on bubble tree compactified instanton moduli spaces, Acta mathematica Sinica. English series (Print) , 26(2), 2010, pp. 209-240
The bubble tree compactified instanton moduli space M..(X) is introduced. Its singularity set Sing . (X) is described. By the standard gluing theory, one can show that M..(X) . Sing . (X) is a topological orbifold. In this paper, we give an argument to construct smooth structures on it