from
Routt ML Jr, Simonian PT, Agnew SG, Mann FA; Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study.; J Orthop Trauma 1996;10(3):171-7:
Routt ML Jr, Simonian PT; Posterior Pelvic Ring Disruptions.; Chapt 37 Master techniques of orthopaedic surgery: Fractures; ed Wiss D; Lippincott-Williams & Wilkins, 2000