Limit-point criterion for singular linear Dirac differential systems

The deficiency index problem of a singular linear Dirac differential system is studied in this paper. Several criterion are presented under which the linear Dirac systems are in the limit-point case or the strong limit-point case. Some of results extensively generalize and improve the previous results obtained by Krall, Hinton and Shaw. Moreover, as a corollary of our results, the Levinson-type criteria for Dirac systems is obtained.