  A Sinc-collocation method has been proposed by Stenger, and he also gave
theoretical analysis of the method in the case of a `scalar' equation. This
paper extends the theoretical results to the case of a `system' of equations.
Furthermore, this paper proposes more efficient method by replacing the
variable transformation employed in Stenger's method. The efficiency is
confirmed by both of theoretical analysis and numerical experiments. In
addition to the existing and newly-proposed Sinc-collocation methods, this
paper also gives similar theoretical results for Sinc-Nystr\"{o}m methods
proposed by Nurmuhammad et al. From a viewpoint of the computational cost, it
turns out that the newly-proposed Sinc-collocation method is the most efficient
among those methods.
