Solutions of the functional tetrahedron equation connected with the local Yang-Baxter equation for the ferro-electric condition

A local (or modified) Yang-Baxter equation (LYBE) gives a functional map from the parameters of the weights in the left-hand side to the parameters of the corresponding weights in the right-hand side of the LYBE. Such maps solve the functional tetrahedron equation. In this Letter, all the maps associated with LYBE's of the ferro-electric type with a single parameter in each weight matrix are classified.