diff --git a/header.tpl b/header.tpl
index 1b8667a..3d8bc42 100644
--- a/header.tpl
+++ b/header.tpl
@@ -189,7 +189,7 @@
           <div class="menu-item">
             <img class="top-icon" src="img/update-icon.svg" alt="update icon"/>
             <a
-            href="https://github.com/NullHypothesis/censorbib/commits/master">Last update: 2023-05-06</a>
+            href="https://github.com/NullHypothesis/censorbib/commits/master">Last update: 2023-05-09</a>
           </div>
           <div class="menu-item">
             <img class="top-icon" src="img/donate-icon.svg" alt="donate icon"/>
diff --git a/references.bib b/references.bib
index 2bea607..470c1f0 100644
--- a/references.bib
+++ b/references.bib
@@ -1,3 +1,12 @@
+@inproceedings{Ververis2021a,
+       title        = {Understanding Internet Censorship in Europe: The Case of Spain},
+       author       = {Vasilis Ververis and Tatiana Ermakova and Marios Isaakidis and Simone Basso and Benjamin Fabian and Stefania Milan},
+       year         = {2021},
+       booktitle    = {13th ACM Web Science Conference 2021},
+       publisher    = {Association for Computing Machinery},
+       url          = {https://doi.org/10.1145/3447535.3462638},
+}
+
 @inproceedings{Ramesh2023a,
 	author = {Reethika Ramesh and Sundara Raman, Ram and Apurva Virkud and Alexandra Dirksen and Armin Huremagic and David Fifield and Dirk Rodenburg and Rod Hynes and Doug Madory and Roya Ensafi},
 	title = {Network Responses to {Russia's} Invasion of {Ukraine} in 2022: A Cautionary Tale for {Internet} Freedom},