@article{KJM_2007_30_1_a8,
     author = {Miloje Rajovi\'c and Rade Stojiljkovi\'c},
     title = {The first, the second, and the third {Liouville} formula and periodical solutions of linear differential equation of the second order},
     journal = {Kragujevac Journal of Mathematics},
     pages = {131 - 139},
     publisher = {mathdoc},
     volume = {30},
     number = {1},
     year = {2007},
     zbl = {1224.34123},
     url = {http://geodesic.mathdoc.fr/item/KJM_2007_30_1_a8/}
}