▁( ), ▁order ▁ 5 7 6 , ▁( D u ▁Val ▁# 2 8 ▁( O / T ; O / T ), ▁Con way ▁ ± 1 / 2 [ O × O ]). ▁ ▁The ▁extended ▁ch iral ▁ icos itet ra chor ic ▁group , ▁[[ 3 , 4 , 3 ]+ ] ▁has ▁order ▁ 1 1 5 2 , ▁( D u ▁Val ▁# 4 6 ▁( O / T ; O / T ) − *, ▁Con way ▁ ± 1 / 2 [ O x O ]. ). ▁C ox eter ▁rel ates ▁this ▁group ▁to ▁the ▁abstract ▁group ▁( 4 , 8 | 2 , 3 ). ▁ ▁Dem it esser actic ▁symmetry ▁▁ ▁Dem it esser actic ▁group ▁– ▁D 4 , ▁[ 3 1 , 1 , 1 ], ▁[ 3 , 3 1 , 1 ] ▁or ▁[ 3 , 3 , 4 , 1 + ], ▁( ▁= ▁), ▁order ▁ 1 9 2 , ▁( D u ▁Val ▁# 4 2 ▁( T / V ; T / V ) − *, ▁Con way ▁ ± 1 / 3 [ T × ]. 2 ), ▁named ▁for ▁the ▁( dem it esser act ) ▁ 4 - demic ube ▁construction ▁of ▁the ▁ 1 6 - cell , ▁ ▁or ▁. ▁There ▁are ▁ 1 2 ▁mirror s ▁in ▁this ▁symmetry ▁group . ▁There ▁are ▁two ▁types ▁of ▁extended ▁symmet ries ▁by ▁adding ▁mirror s : ▁< [ 3