The removal of the smallest possible number of symmetry elements from a molecule with (ref. 1) or without (ref. 2) the restriction to pointwise substitution.
1. K. Mislow and J. Siegel, J. Am. Chem. Soc. 106, 3319-3328 (1984)
2. E.A. Halevi, J. Chem. Res. (S) 206-207 (1985)