@misc{10_4153_CMB_2002_004_6,
     title = {Modular {Equations} and {Discrete,} {Genus-Zero} {Subgroups} of {SL(2,} {R)} {Containing} {\ensuremath{\Gamma}(N)}},
     journal = {Canadian mathematical bulletin},
     pages = {36--45},
     year = {2002},
     volume = {45},
     number = {1},
     doi = {10.4153/CMB-2002-004-6},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2002-004-6/}
}