Issue No.06 - June (1969 vol.18)
F.M. Brown , Dept. of Elec. Engrg. Air Force Institute of Technology
A recent note by Soudack  discusses the application of Levine's method of canonical analog programming  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."
F.M. Brown, "Comment on "Canonical Programming of Nonlinear and Time-Varying Differential Equations"", IEEE Transactions on Computers, vol.18, no. 6, pp. 566, June 1969, doi:10.1109/T-C.1969.222713