@unpublished{HuichengWitt2008,
  author  = {Yin Huicheng and Ingo Witt},
  title   = {Global singularity structure of weak solutions to 3-D semilinear dispersive wave equations with discontinuous initial data},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(2002) 21},
  year    = {2008},
}