International Conference on Numerical Analysis and Applied Mathematics 2010, ICNAAM-2010, Rhodes, Greece, 19 - 25 September 2010, vol.1281, pp.1148-1151
In this work, subgroups of a special class of discrete subgroups of PLS(2,R), namely the ones of the first kind with genus 0, have been studied. We establish a technique to compute the genus of these subgroups in terms of the genus of easier groups. The method established here can be used for triangle groups, surface groups and Hecke groups (including the well-known modular group). © 2010 American Institute of Physics.