A\left(e_{i1},e_{i2},\dots,e_{in}\right)=\sum_{j=1}^k\left(\sum_{i_1=1}^n\sum_{i_2=1}^n\dots\sum_{i_m=1}^n a^j_{i_1,i_2,\dots,i_m} \xi_{1,i_1}\xi_{2,i_2}\dots\xi_{m,i_m}\right)f_j