1- https://www.zoomit.ir/health-medical/387200-how-vladimir-demikhov-made-two-headed-dog/
2- https://www.eligasht.com/Blog/travelguide/%D8%AA%D9%86%D9%87%D8%A7%D8%AA%D8%B1%DB%8C%D9%86-%D9%86%D9%87%D9%86%DA%AF-%D8%AF%D9%86%DB%8C%D8%A7/