@article{MV_1953_5_3-4_a1,
     author = {{\DJ}. Kurepa},
     title = {On some coupled operators in ordered sets},
     journal = {Matemati\v{c}ki vesnik},
     pages = {15 },
     publisher = {mathdoc},
     volume = {5},
     number = {3-4},
     year = {1953},
     url = {http://geodesic.mathdoc.fr/item/MV_1953_5_3-4_a1/}
}