diff --git a/properties/P000075.md b/properties/P000075.md
index 6ab34a0b5..c651ba62f 100644
--- a/properties/P000075.md
+++ b/properties/P000075.md
@@ -8,8 +8,6 @@ refs:
   name: Spectral spaces (Dickmann, Schwartz, Tressl)
 - mr: 861951
   name: Stone spaces (Johnstone)
-- mr: 1077251
-  name: General topology I (Arkhangelʹskiĭ, Pontryagin)
 - wikipedia: Spectral_space
   name: Spectral space on Wikipedia
 ---
diff --git a/theorems/T000531.md b/theorems/T000531.md
index 1e7181eca..e408109af 100644
--- a/theorems/T000531.md
+++ b/theorems/T000531.md
@@ -9,8 +9,6 @@ refs:
   name: Stone spaces (Johnstone)
 - wikipedia: Stone's_representation_theorem_for_Boolean_algebras
   name: Stone's representation theorem for Boolean algebras on Wikipedia
-- wikipedia: Boolean_ring
-  name: Boolean ring on Wikipedia
 - wikipedia: Spectral_space
   name: Spectral space on Wikipedia
 ---