diff --git a/2015/muth/machine_beaver_4_2.h b/2015/muth/machine_beaver_4_2.h
index 13ad467c4..f0fac1373 100644
--- a/2015/muth/machine_beaver_4_2.h
+++ b/2015/muth/machine_beaver_4_2.h
@@ -1,5 +1,5 @@
 /*
- * 4 state, 2 symbol busy beaver, http://www.logique.jussieu.fr/~michel/ha.html#tm42
+ * 4 state, 2 symbol busy beaver, https://web.archive.org/web/20150926094245/http://www.logique.jussieu.fr/~michel/ha.html#tm42
  *
  * halts after 107 steps
  */
diff --git a/2015/muth/machine_champ_2_4.h b/2015/muth/machine_champ_2_4.h
index 77d437d8e..24a8533d3 100644
--- a/2015/muth/machine_champ_2_4.h
+++ b/2015/muth/machine_champ_2_4.h
@@ -1,5 +1,5 @@
 /*
- * 2 state, 4 symbol current champion, http://www.logique.jussieu.fr/~michel/ha.html#tm24
+ * 2 state, 4 symbol current champion, https://web.archive.org/web/20150926094245/http://www.logique.jussieu.fr/~michel/ha.html#tm24
  *
  * halts after 3932964 steps
  */
diff --git a/2015/muth/machine_chaos_5_2.h b/2015/muth/machine_chaos_5_2.h
index d16b9b4d4..1180a4e0a 100644
--- a/2015/muth/machine_chaos_5_2.h
+++ b/2015/muth/machine_chaos_5_2.h
@@ -1,7 +1,7 @@
 /*
- * chaos machine, http://www.drb.insel.de/~heiner/BB/mabu90.html
+ * chaos machine, https://web.archive.org/web/20131104160623/http://www.drb.insel.de/~heiner/BB/mabu90.html
  *
- * does not halt (http://www.drb.insel.de/~heiner/BB/TM4-proof.txt)
+ * does not halt (https://web.archive.org/web/20131104203330/http://www.drb.insel.de/~heiner/BB/TM4-proof.txt)
  */
 
 #define sym_1(sym, _1) sym
diff --git a/2015/muth/machine_cmplx_5_2.h b/2015/muth/machine_cmplx_5_2.h
index 27908da4b..7874f3248 100644
--- a/2015/muth/machine_cmplx_5_2.h
+++ b/2015/muth/machine_cmplx_5_2.h
@@ -1,5 +1,5 @@
 /*
- * complex machine, http://www.drb.insel.de/~heiner/BB/mabu90.html
+ * complex machine, https://web.archive.org/web/20131104160623/http://www.drb.insel.de/~heiner/BB/mabu90.html
  */
 
 #define sym_1(sym, _1) sym
diff --git a/2015/muth/machine_count_5_2.h b/2015/muth/machine_count_5_2.h
index ee9b9a3ce..e006207d5 100644
--- a/2015/muth/machine_count_5_2.h
+++ b/2015/muth/machine_count_5_2.h
@@ -1,5 +1,5 @@
 /*
- * counting machine, http://www.drb.insel.de/~heiner/BB/mabu90.html
+ * counting machine, https://web.archive.org/web/20131104160623/http://www.drb.insel.de/~heiner/BB/mabu90.html
  *
  * does not halt
  */
diff --git a/2015/muth/machine_great_3_2.h b/2015/muth/machine_great_3_2.h
index f4ffbe797..07596f5a3 100644
--- a/2015/muth/machine_great_3_2.h
+++ b/2015/muth/machine_great_3_2.h
@@ -1,5 +1,5 @@
 /*
- * greater machine, http://www.drb.insel.de/~heiner/BB/mabu90.html
+ * greater machine, https://web.archive.org/web/20131104160623/http://www.drb.insel.de/~heiner/BB/mabu90.html
  *
  * does not halt
  */
diff --git a/2015/muth/machine_ru_2_4.h b/2015/muth/machine_ru_2_4.h
index e9523be82..3dd5768f8 100644
--- a/2015/muth/machine_ru_2_4.h
+++ b/2015/muth/machine_ru_2_4.h
@@ -1,5 +1,5 @@
 /*
- * 2 state, 4 symbol current runner-up, http://www.logique.jussieu.fr/~michel/ha.html#tm24
+ * 2 state, 4 symbol current runner-up, https://web.archive.org/web/20150926094245/http://www.logique.jussieu.fr/~michel/ha.html#tm24
  *
  * halts after 7195 steps
  */