@TechReport{      Hack:1976:DQP:889753,
  Author        = "Hack, M.",
  Address       = "Cambridge, MA, USA",
  date-added    = "2013-09-25 10:29:46 +0000",
  date-modified = "2013-09-25 10:30:04 +0000",
  Keywords      = "Petri nets",
  Publisher     = "Massachusetts Institute of Technology",
  source        = "http://www.ncstrl.org:8900/ncstrl/servlet/search?formname=detail\&id=oai\%3Ancstrlh\%3Amitai\%3AMIT-LCS\%2F\%2FMIT\%2FLCS\%2FTR-161",
  Title         = "Decidability Questions for Petri Nets",
  Year          = "1976",
  File          = "DECIDABILITY QUESTIONS FOR PETRI NETS - Hack (0) (0) - a - a - x.pdf"
}

@TechReport{ Hack:1976:DQP:889753, Author = "Hack, M.", Address = "Cambridge, MA, USA", date-added = "2013-09-25 10:29:46 +0000", date-modified = "2013-09-25 10:30:04 +0000", Keywords = "Petri nets", Publisher = "Massachusetts Institute of Technology", source = "http://www.ncstrl.org:8900/ncstrl/servlet/search?formname=detail\&id=oai\%3Ancstrlh\%3Amitai\%3AMIT-LCS\%2F\%2FMIT\%2FLCS\%2FTR-161", Title = "Decidability Questions for Petri Nets", Year = "1976", File = "DECIDABILITY QUESTIONS FOR PETRI NETS - Hack (0) (0) - a - a - x.pdf" }