diff --git a/src/main.cc b/src/main.cc
index d5e780b..effde50 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -3,6 +3,8 @@
 #define GLFW_INCLUDE_NONE
 #include "GLFW/glfw3.h"
 
+//http://seshbot.com/blog/2015/05/05/an-introduction-to-opengl-getting-started/
+
 static void key_callback(GLFWwindow *w, int key, int scancode, int action, int mods) {
     if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS) {
         glfwSetWindowShouldClose(w, GL_TRUE);