@article{10_1017_S0017089510000790,
     author = {LI, YONGKUN and XU, ERLIANG},
     title = {THREE {POSITIVE} {PERIODIC} {SOLUTIONS} {FOR} {DYNAMIC} {EQUATIONS} {WITH} {PIECEWISE} {CONSTANT} {ARGUMENT} {AND} {IMPULSE} {ON} {TIME} {SCALES*}},
     journal = {Glasgow mathematical journal},
     pages = {369--377},
     year = {2011},
     volume = {53},
     number = {2},
     doi = {10.1017/S0017089510000790},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089510000790/}
}