@article{10_4064_aa_40_2_217_227,
     author = {L. Parson},
     title = {On the invariants of the {Hecke} groups},
     journal = {Acta Arithmetica},
     pages = {217--227},
     publisher = {mathdoc},
     volume = {40},
     number = {2},
     year = {1981},
     doi = {10.4064/aa-40-2-217-227},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa-40-2-217-227/}
}