diff --git a/bib/sivanov-extra.bib b/bib/sivanov-extra.bib
index 24f242e..9b4c548 100644
--- a/bib/sivanov-extra.bib
+++ b/bib/sivanov-extra.bib
@@ -1,3 +1,13 @@
+@techreport{AlhazovFI2016,
+author={Artiom Alhazov and Rudolf Freund and Sergiu Ivanov},
+title={Polymorphic P Systems: A Survey},
+booktitle={Bulletin of the International Membrane Computing Society},
+pages={79--101},
+publisher={IMCS},
+volume={Number 2},
+year={December 2016}
+}
+
 @inproceedings{SegretainTGI2021,
 author={Segretain, R{\'e}mi and Trilling, Laurent and Glade, Nicolas and Ivanov, Sergiu},
 title={Who Plays Complex Music? On the Correlations Between Structural