Abstract
In an 1885 paper, E. Picard defined a subgroup Tau(Lambda) of PU(2,1) generated by monodromies and depending on parameters Lambda = (lambda(1),lambda(2),lambda(3),lambda(4)), 0 < lambda(i) < 1, < lambda(i) < 3, lambda(i) + lambda(j) >/= 1, 1