Counterexample to boundary regularity of a strongly pseudoconvex CR   submanifold: An addendum to the paper of Harvey-Lawson
  The purpose of this paper is to give a counterexample of Theorem 10.4 in [Ann. of Math. 102 (1975), 223-290]. In the Harvey-Lawson paper, a global result is claimed, but only a local result is proven. This theorem has had a big impact on CR geometry for almost a quarter of a century because one can use the theory of isolated singularities to study the theory of CR manifolds and vice versa. 
Hing Sun Luk, Stephen S.-T. Yau