@article {MR0282347,
    AUTHOR = {Siwiec, Frank and Mancuso, Vincent J.},
     TITLE = {Relations among certain mappings and conditions for their
              equivalence},
   JOURNAL = {General Topology and Appl.},
  FJOURNAL = {General Topology and its Applications},
    VOLUME = {1},
      YEAR = {1971},
    NUMBER = {1},
     PAGES = {33--41},
      ISSN = {0016-660X},
   MRCLASS = {54.60},
  MRNUMBER = {282347},
MRREVIEWER = {Edwin\ Duda},
}


@article {MR0275387,
    AUTHOR = {Michael, Ernest},
     TITLE = {A theorem on pefect maps},
   JOURNAL = {Proc. Amer. Math. Soc.},
  FJOURNAL = {Proceedings of the American Mathematical Society},
    VOLUME = {28},
      YEAR = {1971},
     PAGES = {633--634},
      ISSN = {0002-9939,1088-6826},
   MRCLASS = {54.60},
  MRNUMBER = {275387},
MRREVIEWER = {Edwin\ Duda},
       DOI = {10.2307/2038028},
       URL = {https://doi.org/10.2307/2038028},
}

@inproceedings {MR1966988,
    AUTHOR = {Chen, Wenyan and Wang, Shutang},
     TITLE = {A sufficient condition for covering projection},
 BOOKTITLE = {Proceedings of the {S}pring {T}opology and {D}ynamical
              {S}ystems {C}onference ({M}orelia {C}ity, 2001)},
   JOURNAL = {Topology Proc.},
  FJOURNAL = {Topology Proceedings},
    VOLUME = {26},
      YEAR = {2001/02},
    NUMBER = {1},
     PAGES = {147--152},
      ISSN = {0146-4124,2331-1290},
   MRCLASS = {54E40 (54C10 57M10)},
  MRNUMBER = {1966988},
}


@article {MR0254818,
    AUTHOR = {Palais, Richard S.},
     TITLE = {When proper maps are closed},
   JOURNAL = {Proc. Amer. Math. Soc.},
  FJOURNAL = {Proceedings of the American Mathematical Society},
    VOLUME = {24},
      YEAR = {1970},
     PAGES = {835--836},
      ISSN = {0002-9939,1088-6826},
   MRCLASS = {54.60},
  MRNUMBER = {254818},
MRREVIEWER = {G.\ S.\ Ungar},
       DOI = {10.2307/2037337},
       URL = {https://doi.org/10.2307/2037337},
}




@article {MR0370471,
    AUTHOR = {Ho, Chung Wu},
     TITLE = {A note on proper maps},
   JOURNAL = {Proc. Amer. Math. Soc.},
  FJOURNAL = {Proceedings of the American Mathematical Society},
    VOLUME = {51},
      YEAR = {1975},
     PAGES = {237--241},
      ISSN = {0002-9939,1088-6826},
   MRCLASS = {54C10},
  MRNUMBER = {370471},
MRREVIEWER = {Edwin\ Duda},
       DOI = {10.2307/2039880},
       URL = {https://doi.org/10.2307/2039880},
}