1. Shillingburg, HT.; Hobo, S.; Whitsett, L.; Jacobi, R.; Brackett, S. Fundamentals of fixed prosthodontics. 3rd ed. Chicago: Quintessence Publishing Co; 1997. p. 124-125.
2. Al-Omari WM, Al-Wahadni AM. Parallelism of abutment teeth on fixed partial dentures. Gen Dent 2009 Jul-Aug; 57(4):444-447.
3. Instrumentation for solving abutment parallelism problems in fixed prosthodontics