
 [No title] 
  For an extension of this matter to the Gaussian numbers, I regarded the two semigroups as hyperbolic motions in the hypberbolic 2space H_2, and their role for a decomposition of the modular group PSL(2,Z). 
  The semigroup H for PSL(2,Z[i]) is generated by 7 elements and is not a free semigroup  the situation increases in complexity. 
  The 7 generators of the semigroup H are: a: (1,1,0,1) b: (1,0,1,1) c: (1,i,0,1) d: (1,0,i,1) e:... 
 www.math.niu.edu /~rusin/knownmath/94/contfra_cpx (862 words) 
