diff --git a/src/search/pdbs/pdb_heuristic.cc b/src/search/pdbs/pdb_heuristic.cc
index f115a3c2d9..74ab54399d 100644
--- a/src/search/pdbs/pdb_heuristic.cc
+++ b/src/search/pdbs/pdb_heuristic.cc
@@ -38,11 +38,21 @@ static basic_string<char> paper_references() {
     return utils::format_conference_reference(
         {"Stefan Edelkamp"},
         "Planning with Pattern Databases",
-        "https://ecp01.icaps-conference.org/papers/A-longpapers/2/edelkamp.pdf",
+        "https://aaai.org/papers/7280-ecp-01-2001/",
         "Proceedings of the Sixth European Conference on Planning (ECP 2001)",
         "84--90",
         "AAAI Press",
-        "2001");
+        "2001") +
+           "For implementation notes, see:" + utils::format_conference_reference(
+        {"Silvan Sievers", "Manuela Ortlieb", "Malte Helmert"},
+        "Efficient Implementation of Pattern Database Heuristics for"
+        " Classical Planning",
+        "https://ai.dmi.unibas.ch/papers/sievers-et-al-socs2012.pdf",
+        "Proceedings of the Fifth Annual Symposium on Combinatorial"
+        " Search (SoCS 2012)",
+        "105-111",
+        "AAAI Press",
+        "2012");
 }
 class PDBHeuristicFeature
     : public plugins::TypedFeature<Evaluator, PDBHeuristic> {
@@ -51,9 +61,9 @@ class PDBHeuristicFeature
         document_subcategory("heuristics_pdb");
         document_title("Pattern database heuristic");
         document_synopsis(
-            "Computes dictionaries for state-to-goal distances in "
+            "Computes goal distance in "
             "state space abstractions based on projections. "
-            "First used in domain independent planning by:"
+            "First used in domain-independent planning by:"
             + paper_references());
 
         add_option<shared_ptr<PatternGenerator>>(