diff --git a/doc/development/open-questions/index.mdwn b/doc/development/open-questions/index.mdwn
index 90adf21b3..9a90256be 100644
--- a/doc/development/open-questions/index.mdwn
+++ b/doc/development/open-questions/index.mdwn
@@ -123,12 +123,14 @@ Discussion of metacognitive strategies that could have computer aides.
     * Primary source, secondary source, etc.
         + Summaries are not the same as the primary source.
         + There have been cases where false information spreads because nobody
-          looks up the original source:
+          looks up the original source or the author uses an invalid source:
             + the diagrams that show different locations on the tongue having
               different tastebuds
             + a journal article that cited a children's novel about Marie
               Antoinette <https://twitter.com/invitinghistory/status/1441080706344443918>,
               <https://vivelareine.tumblr.com/post/663173336356061184>
+            + this thread shows step-by-step how to source historical data
+              <https://twitter.com/rauchway/status/1167142811952566272>
 - Thinking routines
     * <https://www.theconsortiumforpubliceducation.org/resource/project-based-learning-resources-pbl/research/>
     * <http://www.pz.harvard.edu/thinking-routines>