Olive, D., Nicolai, H., & Olive, D. I. (2001). The Principal SO(1,2) subalgebra of a hyperbolic Kac-Moody algebra. Letters in Mathematical Physics, 58(2), pp. 141-152. doi:10.1023/A:1013389001951

Olive, David, H. Nicolai, and D. I. Olive. "The Principal SO(1,2) Subalgebra of a Hyperbolic Kac-Moody Algebra." Letters in Mathematical Physics 58, no. 2 (2001): 141-152.

Olive, David, H. Nicolai, and D. I. Olive. "The Principal SO(1,2) Subalgebra of a Hyperbolic Kac-Moody Algebra." Letters in Mathematical Physics 58.2 (2001): 141-152.