CR singularities of real threefolds in C^4

Adam Coffman

article abstract

CR singularities of real threefolds in C^4 are classified by using
holomorphic coordinate changes to transform the quadratic part of the
real defining equations into one of a list of normal forms.  In the
non-degenerate case, it is shown that a real analytic manifold near a
CR singular point is formally equivalent to a real algebraic model.
Some degenerate cases also have this property.