The harmonic balance technique at first and second order is applied to three retarded delay-differential equations, comparing the results when possible with analytical results. For a first order equation with a fixed delay in linear and cubic terms, the first and second order harmonic balance solutions are compared with an expansion of Pinney (near a bifurcation point in the coefficient of the linear term) and with an exact solution of Dormayer. Another first order equation with a delayed cubic term is studied, for which there is a bifurcation as the delay increases, and a second order equation with a linear delayed term. Also the first order harmonic balance and a perturbation result for the sunflower equation are compared. (C) 1995 Academic Press Limited [References: 24]
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