@article{10_4064_aa_90_1_1_16,
     author = {Wenguang Zhai and Xiaodong Cao},
     title = {On the number of coprime integer pairs within a circle},
     journal = {Acta Arithmetica},
     pages = {1--16},
     publisher = {mathdoc},
     volume = {90},
     number = {1},
     year = {1999},
     doi = {10.4064/aa-90-1-1-16},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-90-1-1-16/}
}