(en) Gerald W. Schwarz, « Smooth functions invariant under the action of a compact Lie group », Topology, vol. 14, , p. 63-68 (MR0370643, zbMATH0297.57015).
(en) Gerald W. Schwarz, « Smooth functions invariant under the action of a compact Lie group », Topology, vol. 14, , p. 63-68 (MR0370643, zbMATH0297.57015).