@unpublished{ChenLi2009,
  author  = {Hua Chen and Ke Li},
  title   = {The existence and regularity of multiple solutions for a class of infinitely degenerate elliptic equations},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(2007) 03},
  year    = {2009},
}