In the treatment of cellulose pulp in connection with bleaching, the pulp is first cooked and, if necessary, oxygen delignified in order to reduce the Kappa number below 24, preferably below 14, and after that the pulp is treated in an acid stage at a pH of 2-5 and at a temperature range of 75-130 C. Based on a result of the voice recognition, a language processing unit, a dialog managing unit and a response generating unit cooperatively create a dialog sentence for exchanging a dialog with the user. % of at least one hydrophilic monomer; greater than 3 wt. This reduces the distance between interference fringes by n, where again n is the number of entangled photons.