@article{GDZPPN002076977,
title = {Angles of a Parallelogram with Vertices in Lattice Points.},
journal = {Elemente der Mathematik},
volume = {24},
year = {1969},
pages = {114-115},
zbl = {0182.37801},
url = {http://dml.mathdoc.fr/item/GDZPPN002076977}
}
Makowski, Andrzej. Angles of a Parallelogram with Vertices in Lattice Points.. Elemente der Mathematik, Tome 24 (1969) pp. 114-115. http://gdmltest.u-ga.fr/item/GDZPPN002076977/