${\displaystyle \left(\begin{array}{ccc}{\mu }_{\text{xx}}& {\mu }_{\text{xy}}& {\mu }_{\text{xz}}\\ \underset{\_}{\underset{\_}{\mu }}={\mu }_{\text{yx}}& {\mu }_{\text{yy}}& {\mu }_{\text{yz}}\\ {\mu }_{\text{zx}}& {\mu }_{\text{zy}}& {\mu }_{\text{zz}}\end{array}\right)}$