摘要
In the referenced paper the existence of heteroclinic orbits of Shil始nikov type is proved by using the undetermined coefficient method, in a three-dimensional quadratic autonomous system. Here we show that the demonstration is incorrect. A misuse of a time-reversibility property leads the authors to consider an odd expression for the first component of the heteroclinic connection. It is evident that this odd expression can never represent the first component of a Shil始nikov heteroclinic connection, an orbit which is necessarily non-symmetric.