diff --git a/index.ipynb b/index.ipynb
index 7e63afc33e08a64e38fbe46cd355ab72d4bc1b3a..148d6a84f1332eec7d18e13b40864b81edcc3260 100644
--- a/index.ipynb
+++ b/index.ipynb
@@ -30,7 +30,7 @@
     "\n",
     "- [J0401 - Unloading with multi-linear bond-slip law](bmcs_course/4_1_PO_multilinear_unloading.ipynb) (PO_BS_ML)\n",
     "- [J0402 - Basic concept of plasticity](bmcs_course/4_2_BS_EP_SH_IK_A.ipynb) (BS_EP_SH_IK_A)\n",
-    "- [J0403 - General time-stepping algorithm](bmcs_course/4_3_BS_EP_SH_IK_N.ipynb) (BS_EP_SH_IK_N)\n",
+    "- [J0403 - EXTRA - General time-stepping algorithm](bmcs_course/4_3_BS_EP_SH_IK_N.ipynb) (BS_EP_SH_IK_N)\n",
     "- [J0404 - Damage framework](bmcs_course)\n",
     "- [J0405 - Iterative numerical simulation](bmcs_course)/4_3_BS_EP_SH_IK_N\n",
     "\n",