@article{10_1017_S0017089503001459,
     author = {DRNOV\v{s}EK, ROMAN},
     title = {A {GENERALIZATION} {OF} {LEVINGER'S} {THEOREM} {TO} {POSITIVE} {KERNEL} {OPERATORS}},
     journal = {Glasgow mathematical journal},
     pages = {545--555},
     year = {2003},
     volume = {45},
     number = {3},
     doi = {10.1017/S0017089503001459},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089503001459/}
}