@article{Margenstern2000,
  author    = {{Margenstern, Maurice}},
  title     = {{Frontier between decidability and undecidability: a survey}},
  journal   = {{Theor. Comput. Sci.}},
  year      = {{2000}},
  volume    = {{231}},
  pages     = {{217--251}},
  note      = {{MR 2001g:03079}},
}