a) I have posted a reference separately.

b) Abstract--Recurrent neural networks are frequently applied to simulate sequence learning applications such as language processing, sensory-motor learning, etc. For this purpose, they often apply a truncated gradient descent (=error correcting) learning algorithm. In order to converge to a solution that is congruent with a target set of sequences, many iterations of sequence presentations and weight adjustments are typically needed. Moreover, there is no guarantee of finding the global minimum of error in a multidimensional error landscape resulting from the discrepancy between target values and the network's prediction.
http://shortify.com/9958


c) http://shortify.com/9959