  The theory of versal normal form has been playing a role in normal form since
the introduction of the concept by V.I. Arnol'd. But there has been no
systematic use of it that is in line with the semidirect character of the group
of formal transformations on formal vector fields, that is, the linear part
should be done completely first, before one computes the nonlinear terms. In
this paper we address this issue by giving a complete description of a first
order calculation in the case of the two- and three-dimensional irreducible
nilpotent cases, which is then followed up by an explicit almost symplectic
calculation to find the transformation to versal normal form in a particular
fluid dynamics problem and in the celestial mechanics \(L_4\) problem.
