@article{10_5817_AM2018_2_65,
     author = {Majumder, Sujoy and Mandal, Rajib},
     title = {On a result of {Zhang} and {Xu} concerning their open problem},
     journal = {Archivum mathematicum},
     pages = {65--89},
     publisher = {mathdoc},
     volume = {54},
     number = {2},
     year = {2018},
     doi = {10.5817/AM2018-2-65},
     mrnumber = {3813736},
     zbl = {06890306},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.5817/AM2018-2-65/}
}