diff --git a/docs/references.bib b/docs/references.bib
index 50095dab..b2c88001 100644
--- a/docs/references.bib
+++ b/docs/references.bib
@@ -386,6 +386,7 @@ @inproceedings{Berkel2015
   title         = "Characterization of printed transmission lines at high frequencies",
   year          = "2015",
   month         = "4",
+  booktitle     = "The 9th European Conference on Antennas and Propagation (EuCAP 2015)",
   publisher     = "The 9th European Conference on Antennas and Propagation (EuCAP 2015)",
   url           = "https://terahertz.tudelft.nl/Research/project.php?id=74\&ti=27",
   venue         = "Lisbon, Portugal"