One folding style with several printable designs (some takes lots of ink). Creator also offers OpenOffice.org Draw templates (Creative-Commons license) to create your own Letterfu design.
R. Drechsler, S. Autexier, und C. Lüth. Dynamics in Logistics: Proceedings of the 5th International Conference LDIC, 2016 Bremen, Germany, Kapitel 1, Springer, Cham, (2017)