where v mj and v mj are the amounts of j-th substrate and j-th product, respectively, in m-th reaction, m = 1, 2, . . . , M . We assume that for every m = 1, 2, ..., M and every j = 1, 2, ..., k either v mj or v mj is equal to 0 (in other words, substance R j is involved in m-th reaction either as substrate or as product).