@article{10_2298_FIL2114743H,
     author = {Beddani Hamid},
     title = {Upper-solution or lower-solution method for {Langevin} equations with n fractional orders},
     journal = {Filomat},
     pages = {4743 },
     year = {2021},
     volume = {35},
     number = {14},
     doi = {10.2298/FIL2114743H},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.2298/FIL2114743H/}
}