diff --git a/literatur.bib b/literatur.bib
index 9339e65..1755141 100644
--- a/literatur.bib
+++ b/literatur.bib
@@ -13175,6 +13175,14 @@ @InProceedings{porteous-et-al-ecp2001
   crossref =     "ecp2001"
 }
 
+@InProceedings{porteous-sebastia-plansig2000,
+  author =       "Julie Porteous and Laura Sebastia",
+  title =        "Extracting and Ordering Landmarks for Planning",
+  booktitle =    "Proceedings of the 19th Workshop of the UK Planning and
+                  Scheduling Special Interest Group (PlanSIG 2000)",
+  year =         "2000"
+}
+
 % Data taken from DBLP
 @InProceedings{poveda-et-al-gecco2019,
   author =       "Guillaume Pov{\'{e}}da and Olivier Regnier{-}Coudert and