@article {MR0221471,
    AUTHOR = {V\"{a}is\"{a}l\"{a}, J.},
     TITLE = {The separability of cartesian products},
   JOURNAL = {Colloq. Math.},
  FJOURNAL = {Colloquium Mathematicum},
    VOLUME = {17},
      YEAR = {1967},
     PAGES = {285--288},
      ISSN = {0010-1354,1730-6302},
   MRCLASS = {54.40},
  MRNUMBER = {221471},
MRREVIEWER = {S.\ A.\ Naimpally},
       DOI = {10.4064/cm-17-2-285-288},
       URL = {https://doi.org/10.4064/cm-17-2-285-288},
}


@article {MR0315649,
    AUTHOR = {Blair, Robert L.},
     TITLE = {The {H}ewitt-{P}ondiczery-{M}arczewski theorem on the density
              character of a product space},
   JOURNAL = {Arch. Math. (Basel)},
  FJOURNAL = {Archiv der Mathematik},
    VOLUME = {23},
      YEAR = {1972},
     PAGES = {422--424},
      ISSN = {0003-889X,1420-8938},
   MRCLASS = {54B10 (54A25)},
  MRNUMBER = {315649},
MRREVIEWER = {W.\ W.\ Comfort},
       DOI = {10.1007/BF01304909},
       URL = {https://doi.org/10.1007/BF01304909},
}