There are four different commutative quarternary rings with identity: Galois field F_4, Z_4, F_2 + uF_2 and F_2 + vF_2. In 1996, V. Pless and Z.

• Galois域F4；整数模4剩余类环Z4；环F2+uF2和环F2+uF2.；V