@article{10_4064_aa101_4_1,
     author = {Nobuhiko Ishida and Noburo Ishii},
     title = {Generators and defining equation of the
modular function field of the group ${\mit\Gamma }_1(N)$},
     journal = {Acta Arithmetica},
     pages = {303--320},
     publisher = {mathdoc},
     volume = {101},
     number = {4},
     year = {2002},
     doi = {10.4064/aa101-4-1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa101-4-1/}
}