@article{PDA_1981_11_1_a1,
     author = {D. Olevi\'c and D. Djurovi\'c},
     title = {The {Periodicity} of {Residuals} $\Delta_{\varphi}$ and $\Delta \theta$ of {The} {Double} {Star} {ADS} 11520},
     journal = {Publications of the Department of Astronomy},
     pages = {15 - 18},
     publisher = {mathdoc},
     volume = {11},
     number = {1},
     year = {1981},
     url = {http://geodesic.mathdoc.fr/item/PDA_1981_11_1_a1/}
}