The Stability of Nonlinear PID Control with Arbitrary Partial-State Knowledge. - Brian Armstrong 002; José A. Gutierrez; Ralph Joseph; Bruce A. Wade (ICRA, 2002)

Stability of Phase-Based Gain Modulation with Designer-Chosen Switch Functions. - Brian S. R. Armstrong; José A. Gutierrez; Bruce A. Wade; Ralph Joseph (Int. J. Robotics Res., 2006)