Comment on “Heteroclinic orbits in Chen circuit with time delay” [Commun. Nonlinear Sci. Numer. Simulat. 15 (2010) 3058–3066]

The authors claim in the abstract of the referenced paper that Existence of Shil’nikov type of heteroclinic orbit in Chen circuit with direct time delay feedback is proved using the undetermined coefficient method. As a result, Shil’nikov criterion guarantees that the circuit has Smale horseshoes and the circuit demonstrates chaos in a rigorous analytical sense. Unfortunately, we show in this comment that their demonstration is incorrect.