1
Olver P J, Pohjanpelto J. Differential invariant algebras of Lie pseudo-groups[J]. Advances in Mathematics, 2009, 222(5): 1746-1792.
2
Ceria M, Mora T, Roggero M, et al. Term-ordering free involutive bases[J]. Journal of Symbolic Computation, 2015, 68(2): 87-108.