Lawton CD, Smith ZA, Nixon AT, Dahdaleh NS, Wong AP, Khanna R, Barnawi A, Fessler RG. The effect of surgical level on self-reported clinical outcomes after minimally invasive transforaminal lumbar interbody fusion: L4-L5 versus L5-S1. World Neurosurg. 2014 Jan; 81(1):177-82.