I. Introduction
Accessibility Lie algebra plays a fundamental role in the investigation of controllability of nonlinear systems [7]. Frobenius’ Theorem and Chow's Theorem are the bridge to connect the accessibility Lie algebra with variety of controllabilities of nonlinear systems. We refer to [11] for Frobenius’ Theorem and to [1] for Chow's Theorem because they provide generalized versions for analytic case, which is suitable for bilinear systems.