Comments, with reply, on "Chaos from third-order phase-locked loops with a slowly varying parameter" by Y.-H. Chu et al

The commenter refers to a third-order nonautonomous differential equation rewritten as a set of three first-order equations used in the work of Y.-H. Chu et al. (see ibid., vol.37, p.1104-15, 1990). He points out inconsistencies in the use of the a´ and k parameters. In their reply, the authors clarify their position and mention that some explanatory material should have been included in the commented paper to avoid the readers´ confusion.<>