The first eigenvalue of the laplacian for a positively curved homogeneous riemannian manifold Hajime Urakawa — 1986 Compositio Mathematica
Yang-Mills connections over compact strongly pseudoconvex CR manifolds. Hajime Urakawa — 1994 Mathematische Zeitschrift
Bounded domains which are isospectral but not congruent Hajime Urakawa — 1982 Annales scientifiques de l'École Normale Supérieure
Morse indices of Yang-Mills connections over the unit sphere Shin Nayatani; Hajime Urakawa — 1995 Compositio Mathematica