@article{AUM_2017_71_2_a5,
     author = {Markowicz, Joanna and Prus, Stanis{\l}aw},
     title = {Properties of modulus of monotonicity and {Opial} property in direct sums},
     journal = {Annales Universitatis Mariae Curie-Sk{\l}odowska. Mathematica },
     publisher = {mathdoc},
     volume = {71},
     number = {2},
     year = {2017},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/AUM_2017_71_2_a5/}
}