in P 1 1 2/n by applying P -1 RP using P = (-b+c,-b-c,a:0,1/2,0) and the row matrix (x,-y,z). In cases where the centering changes in going to the final setting, we must be sure to also add any new centering that arises. For example, for the non-reference setting C 4 m g1 (space group 100, P 4 b m),