In their paper [1], Tsoi and Tan present what they call a "canonical form", which they claim to be identical to that proposed in Nerrand et al [2]. They also claim that the algorithm which they present can be applied to any recurrent neural network. In the present comment, we disprove both claims. Back in 1993, Nerrand et al. [2] proposed a general approach to the training of recurrent networks, either adaptively (on-line) or non-adaptively (off-line). One of the main points