@BOOK( Bag1979,
  author = "Bilbo Baggins",
  title = "Introduction to the theory, languages, and routing",
  publisher = "Mulison-Wesley",
  address = "Writing, Massachusetts",
  year = 1979,
)

@BOOK( Bag1990,
  author = "Bilbo Baggins",
  title = "Introduction to the theory of bags",
  publisher = "Mulison-Wesley",
  address = "Writing, Massachusetts",
  year = 1990,
)