Generic unfolding of the nilpotent saddle of codimension four

In this paper we study the generic unfoldings of the nilpotent saddle of codimension four. It gives us the opportunity of presenting the totality of techniques that are currently being used in the field, and of surveying technical problems that need to be solved. Moreover, as can be seen in the next section, the case under consideration is more interesting than merely being the next one in a systematic treatment.