Geodesic flow and two (super) component analog of the Camassa-Holm equation. Guha, Partha; Olver, Peter J. — 2006 SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]
Differential invariants of conformal and projective surfaces. Hubert, Evelyne; Olver, Peter J. — 2007 SIGMA. Symmetry, Integrability and Geometry: Methods and Applications [electronic only]