From Online Dictionary of Crystallography
Groupes de Sohncke (Fr), Gruppi di Sohncke (It).
Sohncke groups are called the 65 three-dimensional space groups containing only operations of the first kind (rotations, rototranslations, translations). Chiral crystal structures, including proteins, occur in these groups, not only in the chiral space groups.
The term comes from Leonhard Sohncke (Halle, 22 February 1842 – München, 1 November 1897), German mathematician.