The Iwasawa invariants and the higher K -groups associated to real quadratic fields. Sumida-Takahashi, Hiroki — 2005 Experimental Mathematics
On Hilbert-Speiser type imaginary quadratic fields Humio Ichimura; Hiroki Sumida-Takahashi — 2009 Acta Arithmetica
Imaginary quadratic fields satisfying the Hilbert-Speiser type condition for a small prime p Humio Ichimura; Hiroki Sumida-Takahashi — 2007 Acta Arithmetica