diff --git a/paper/references.bib b/paper/references.bib
index 0cc753ff..3ac30deb 100644
--- a/paper/references.bib
+++ b/paper/references.bib
@@ -138,7 +138,6 @@ @article{Ferretti2011NewAlgorithmProcessing
   publisher = {IEEE},
   issn = {01962892},
   doi = {10.1109/TGRS.2011.2124465},
-  isbn = {0196-2892},
   keywords = {1pass,Coherence matrix,distributed scatterers (DS),InSAR,permanent scatterers,space-adaptive filtering}
 }