diff --git a/books/history/ibm-holocaust.md b/books/history/ibm-holocaust.md
index 11ff4786075b75b874c70e5814b7f2d6f69d951e..6205c1780bc6eafc125cea46b680b3586f01a859 100644
--- a/books/history/ibm-holocaust.md
+++ b/books/history/ibm-holocaust.md
@@ -1895,4 +1895,26 @@ That was before the US entering the war.
 * Investigation that required "Holocaust knowledge with an emphasis on Hitler-era finance, added to information-technology expertise, sifted through the dogged techniques of an investigative reporter", 454.
 * Local and central processing facilities -- like Berlin and Oranienburg, 455.
 
+## Further reading
+
+* Quantifying the Holocaust: Hyperintense kill rates during the Nazi genocide:
+  * https://www.buzzfeednews.com/article/danvergano/nazi-holocaust-death-rate-underestimated
+  * http://advances.sciencemag.org/content/5/1/eaau7292
+  * http://advances.sciencemag.org/content/5/1/eaau7292/tab-pdf
+  * https://encyclopedia.ushmm.org/content/en/article/operation-reinhard-einsatz-reinhard
+
+    Operation Reinhard (1942–1943) was the largest single murder campaign of the
+    Holocaust, during which some 1.7 million Jews from German-occupied Poland were
+    murdered by the Nazis. Most perished in gas chambers at the death camps Belzec,
+    Sobibor, and Treblinka. However, the tempo, kill rates, and spatial dynamics of
+    these events were poorly documented. Using an unusual dataset originating from
+    railway transportation records, this study identifies an extreme phase of
+    hyperintense killing when >1.47 million Jews—more than 25% of the Jews killed
+    in all 6 years of World War II—were murdered by the Nazis in an intense,100-day
+    (~3-month) surge.  Operation Reinhard is shown to be an extreme event, based on
+    kill rate, number, and proportion (>99.9%) of the population murdered in camps,
+    highlighting its singularly violent character, even compared to other more
+    recent genocides. The Holocaust kill rate is some 10 times higher than
+    estimates suggested by authorities on comparative genocide.
+
 [[!tag tecnology history sociology]]