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@Book{            Siefkes,
  Author        = "Siefkes, Dirk",
  date-added    = "2020-04-10 11:07:26 +0200",
  date-modified = "2020-04-10 11:07:26 +0200",
  Publisher     = "Springer-Verlag",
  Title         = {Decidable Theories I - B{\"u}chi's Monadic Second Order Successor Arithmetic},
  Year          = "1970",
  File          = "Decidable Theories I - Büchi's Monadic Second Order Successor Arithmetic - Siefkes (0) (0) - a - a.pdf"
}

@Book{ Siefkes, Author = "Siefkes, Dirk", date-added = "2020-04-10 11:07:26 +0200", date-modified = "2020-04-10 11:07:26 +0200", Publisher = "Springer-Verlag", Title = {Decidable Theories I - B{\"u}chi's Monadic Second Order Successor Arithmetic}, Year = "1970", File = "Decidable Theories I - Büchi's Monadic Second Order Successor Arithmetic - Siefkes (0) (0) - a - a.pdf" }