diff --git a/md/intro_about.md b/md/intro_about.md
index 59855bec95..d8a3557e15 100644
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Further Details
===============
-More detailed information on how to use this web application. Further reading on the data from the global population projections by age, sex and education is provided in Lutz, Goujon, KC, Stonawski, and Stilianakis (Eds.) (2018) .
+More detailed information on how to use this web application. Further reading on the data from the global population projections by age, sex and education is provided in Lutz, Goujon, KC, Stonawski, and Stilianakis (Eds.) (2018) and in Speringer et al. (2018) for the reconstruction. Further features about the methodology can be found in Lutz, Butz, and K.C. (2014).