In this paper we shall define certain loop groups which act on simply connected -surfaces in space forms preserving conformality, and obtain a criterion for these group actions to be equivariant.
Atsushi FUJIOKA. "Actions of loop groups on simply connected -surfaces in space forms." J. Math. Soc. Japan 50 (4) 819 - 829, October, 1998. https://doi.org/10.2969/jmsj/05040819