@article{ELMA_1969__24_140942,
     author = {Andrzej Makowski},
     title = {Angles of a {Parallelogram} with {Vertices} in {Lattice} {Points.}},
     journal = {Elemente der Mathematik},
     pages = {114--115},
     publisher = {mathdoc},
     volume = {24},
     year = {1969},
     zbl = {0182.37801},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1969__24_140942/}
}