In order to precisely analyse the possible pitfalls when transforming from Z-matrix to cartesian coordinates, it is advantageous to adopt the view of the Self-Normalizing Natural Extension Reference Frame (SN-NeRF) as described by Parsons et al and subsequently parallized by AlQuraishi. The Z-matrix entries for an atom are interpreted as spherical coordinates and an atom is put into the canonical reference frame. This frame is then rotated and translated into the orthonormalised, righthanded reference frame M which is spanned locally by the three reference atoms. In the following the variables r, α, δ should canonically stand for distance, angle and dihedral. The index variables i, b, a, d should canonically stand for the index of the atom to be inserted and its bond, angle, and dihedral defining atom. v i , v b , ... should be the respective positions. By defining b, a, and d we implicitly assumed that there are three reference atoms, which is not the case for the first three atoms. Practically this implies usually that the upper right triangle of a Z-matrix is left empty and that there exist conventions for putting the first atom into the origin, align the second atom along the z-axis etc. (Hence the name Z-matrix). In this work the information about the absolute positions in cartesian space was stored with an approach similar to Hoft et al. In the first three rows the origin and canonical unit vectors can be treated as if they were reference atoms, to specify translational and rotational degrees of freedom. These fixed points in cartesian space that are used to specify the absolute position will be called absolute references.