gap> mat := [[0,1,0],[1,0,0],[0,0,1]]*Z(169)^0; [ [ 0*Z(13), Z(13)^0, 0*Z(13) ], [ Z(13)^0, 0*Z(13), 0*Z(13) ], [ 0*Z(13), 0*Z(13), Z(13)^0 ] ] gap> phi := PolarityOfProjectiveSpace(mat,GF(169)); <polarity of PG(2, GF(13^2)), >