@InProceedings{   Ryll-Nardzewski:1959,
  Author        = "Ryll-Nardzewski, Czes{\l}aw",
  BookTitle     = "Bull. Acad. Polon. Sci. Ser. Sci. Math. Astr. Phys.",
  date-added    = "2020-04-29 10:51:31 +0200",
  date-modified = "2020-04-29 10:52:43 +0200",
  Pages         = "545---548",
  Title         = "On the categoricity in power $\leq \aleph\_0$",
  Volume        = "7",
  Year          = "1959"
}

@InProceedings{ Ryll-Nardzewski:1959, Author = "Ryll-Nardzewski, Czes{\l}aw", BookTitle = "Bull. Acad. Polon. Sci. Ser. Sci. Math. Astr. Phys.", date-added = "2020-04-29 10:51:31 +0200", date-modified = "2020-04-29 10:52:43 +0200", Pages = "545---548", Title = "On the categoricity in power $\leq \aleph_0$", Volume = "7", Year = "1959" }