An algorithm for division of powerseries

An algorithm is given to compute a solution (b ₀, ...,b _n) of $$\sum\limits_0^n {a_i t^i } \sum\limits_0^n {b_i t^i } \equiv \sum\limits_0^n {c_i t^i } (t^{n + 1} )$$ froma ₀, ..., a_n, c₀, ..., c_n. It needs less than 7n multiplications, where multiplications with a skalar from an infinite subfield are not counted.