Routinely, the Dirac equation is decoupled into two alternative
ordinary linear differential Schr\"{o}dinger-like equations
(viz., eqs. (2.8) and (2.10)). The first few simplest forms of
the invasive ``quasi-exact'' (i.e., exponential times
polynomial) ansatz for a single, exceptional bound-state wave
function are then inserted yielding the first few simplest
forms of the necessary algebraic consistency restrictions
imposed upon the parameters.

MR2980407 Hassanabadi, H.; Maghsoodi, E.; Zarrinkamar, S.; Rahimov, H. 
Dirac equation under scalar, vector, and tensor Cornell interactions. 
Adv. High Energy Phys. 2012, Art. ID 707041, 17 pp. 81Qxx