Comment on "Canonical Programming of Nonlinear and Time-Varying Differential Equations"

A recent note by Soudack [1] discusses the application of Levine\´s method of canonical analog programming [2] to nonlinear and time-varying differential equations. Assuming that only the ai(t) are time-varying, Soudack states that canonical programming cannot be applied to the differential equation E ai(t) piy(t) = E bj(t) piu(t) (1) unless the condition m < n-q (2) is satisfied, where q is "the order of the highest derivative where a nonlinearity occurs, or is the highest derivative multiplied by a time-varying coefficient."