1. School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States.
2. Department of Neurosurgery, The University of Oklahoma, Health Sciences Center, Oklahoma City, Oklahoma, United States.
3. Department of Mathematics, The University of Texas Permian Basin, Odessa, United States.
4. Department of Pediatrics, Division of Neurosurgery, Texas Tech University Health Sciences Center, Lubbock, Texas, United States.