Generators and equations for modular function fields of principal congruence subgroups Nobuhiko Ishida — 1998 Acta Arithmetica
The Equations for Modular Function Fields of Principal congruence subgroups of prime level. Nobuhiko Ishida; Noburo Ishii — 1996 Manuscripta mathematica
Generators and defining equation of the modular function field of the group Γ₁(N) Nobuhiko Ishida; Noburo Ishii — 2002 Acta Arithmetica