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--- a/README.md
+++ b/README.md
@@ -24,7 +24,8 @@ COVID-19/influenza IFR estimates.
 The COVID-19 IFR curves represent these estimates:
 
 1. ENE-COVID Spanish serosurvey (calculated by `calc_ifr.py`, see [this section](#calculating-the-age-stratified-ifr-of-covid-19-from-the-spanish-ene-covid-study))
-1. [US CDC COVID-19 Pandemic Planning Scenarios](https://web.archive.org/web/20200911222029/https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html) (table 1)
+1. [US CDC COVID-19 Pandemic Planning Scenarios](https://web.archive.org/web/20200911222029/https://www.cdc.gov/coronavirus/2019-ncov/hcp/planning-scenarios.html) (table 1);
+  which is based on [Estimation of SARS-CoV-2 mortality during the early stages of an epidemic: A modeling study in Hubei, China, and six regions in Europe](https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003189)
 1. [Verity et al.: Estimates of the severity of coronavirus disease 2019: a model-based analysis](https://www.thelancet.com/journals/laninf/article/PIIS1473-3099%2820%2930243-7/fulltext) (table 1)
 1. [Levin et al.: Assessing the age specificity of infection fatality rates for COVID-19: systematic review, meta-analysis, and public policy implications](https://www.medrxiv.org/content/10.1101/2020.07.23.20160895v5) (table 3)
 1. [Perez-Saez et al.: Serology-informed estimates of SARS-CoV-2 infection fatality risk in Geneva, Switzerland](https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30584-3/fulltext)