https://go.fold3.com/holocaust_camps/
https://www.ushmm.org/wlc/en/article.php?ModuleId=10005189
https://www.jewishgen.org/forgottencamps/Camps/BelzecEng.html
http://auschwitz.org/en/history/auschwitz-and-shoah/the-extermination-procedure-in-the-gas-chambers
https://www.ushmm.org/outreach/en/article.php?ModuleId=10007724
https://www.ushmm.org/wlc/en/article.php?ModuleId=10005189
https://www.jewishgen.org/forgottencamps/Camps/BelzecEng.html
http://auschwitz.org/en/history/auschwitz-and-shoah/the-extermination-procedure-in-the-gas-chambers
https://www.ushmm.org/outreach/en/article.php?ModuleId=10007724