Update README.md

Author: AdarshRevankar

README.md

@@ -24,7 +24,7 @@ OpenGL project which consists of 3D environment, to demonstrate assembly and dis
  glut.h ( freeglut.h )
 
 # References
- [1]. Basic 3D World Setup - [lighthouse3d.com](http://www.lighthouse3d.com/tutorials/glut-tutorial/).
- [2]. Basic OpenGL function's introduction - [khronos.org](https://www.khronos.org/).
- [3]. Texture Mapping - [youtube.com](https://www.youtube.com/watch?v=Eh0HeTCCgnE&t=452s).
- [4]. Textbook for understanding structure of OpenGL - [Computer Graphics With OpenGL - Donald Hearn & Pauline Baker](https://doc.lagout.org/programmation/OpenGL/Computer%20Graphics%20with%20OpenGL%20%284th%20ed.%29%20%5BHearn%2C%20Baker%20%26%20Carithers%202013%5D.pdf).
+ 1. Basic 3D World Setup - [lighthouse3d.com](http://www.lighthouse3d.com/tutorials/glut-tutorial/).
+ 2. Basic OpenGL function's introduction - [khronos.org](https://www.khronos.org/).
+ 3. Texture Mapping - [youtube.com](https://www.youtube.com/watch?v=Eh0HeTCCgnE&t=452s).
+ 4. Textbook for understanding structure of OpenGL - [Computer Graphics With OpenGL - Donald Hearn & Pauline Baker](https://doc.lagout.org/programmation/OpenGL/Computer%20Graphics%20with%20OpenGL%20%284th%20ed.%29%20%5BHearn%2C%20Baker%20%26%20Carithers%202013%5D.pdf).