Let us now assume that [x.sup.(N).sub.1], ..., [x.sup.(N).sub.N] are the zeros of the polynomial [p.sub.N](x) from the orthogonal family [{[p.sub.v](x)}.sup.[infinity].sub.v=0], while [mathematical expression not reproducible] ,..., [mathematical expression not reproducible] are the zeros of the polynomial [mathematical expression not reproducible].