declare E3 {
    mode=0,
    latex="E^{(3)}_{0}",
}

declare E3square {
    mode=0,
    latex="(E^{(3)}_{0})^{2}",
}

declare H {
    mode=4,
    latex="H",
}

E3 = sum_abcijk(H_ijab * H_kbic * H_ackj);

E3square = sum_abcijkdeflmn(H_ijab * H_kbic * H_ackj * H_lmde * H_nelf * H_dfnm);

