diff --git a/Trigonometry/.ipynb_checkpoints/Easy_Way_to_Memorize_Unit_Circle-checkpoint.ipynb b/Trigonometry/.ipynb_checkpoints/Easy_Way_to_Memorize_Unit_Circle-checkpoint.ipynb
index 23d4a5d..84bf912 100644
--- a/Trigonometry/.ipynb_checkpoints/Easy_Way_to_Memorize_Unit_Circle-checkpoint.ipynb
+++ b/Trigonometry/.ipynb_checkpoints/Easy_Way_to_Memorize_Unit_Circle-checkpoint.ipynb
@@ -10,6 +10,8 @@
     "\n",
     "<p class='lead'>All you have to remember is: $0, 1, 2, 3, \\text{ and } 4$ and $\\frac{\\sqrt{x}}{2}$.</p>\n",
     "\n",
+    "<cite>Credit and gratitude for this technique must be given to Eli Hibit ([@pwnphysics](https://twitter.com/pwnphysics)), who described it on his podcast, [PWN Physics](http://t.co/NPRzrTzIfD).</cite>\n",
+    "\n",
     "---"
    ]
   },
diff --git a/Trigonometry/Easy_Way_to_Memorize_Unit_Circle.ipynb b/Trigonometry/Easy_Way_to_Memorize_Unit_Circle.ipynb
index 23d4a5d..84bf912 100644
--- a/Trigonometry/Easy_Way_to_Memorize_Unit_Circle.ipynb
+++ b/Trigonometry/Easy_Way_to_Memorize_Unit_Circle.ipynb
@@ -10,6 +10,8 @@
     "\n",
     "<p class='lead'>All you have to remember is: $0, 1, 2, 3, \\text{ and } 4$ and $\\frac{\\sqrt{x}}{2}$.</p>\n",
     "\n",
+    "<cite>Credit and gratitude for this technique must be given to Eli Hibit ([@pwnphysics](https://twitter.com/pwnphysics)), who described it on his podcast, [PWN Physics](http://t.co/NPRzrTzIfD).</cite>\n",
+    "\n",
     "---"
    ]
   },