19. The process according to claim 13, wherein the aque› ous composition additionally comprises at least one further additive selected from the group consisting of aluminum sul› fate, aluminum nitrate, polyaluminum chloride (PAC), alu› minum hydroxide chloride, organic precipitant, biocide, deaerator, defoamer, dispersant, adsorbent, fixative, retention aid, drainage accelerant, dye, optical brightener, internal siz› ing agent, wet strength agent, dry strength enhancer and inter› nal wet web strength polymer (IWWS). 

20. The process according to claim 13, wherein the aque› ous composition additionally comprises at least one inorganic filler selected from the group consisting of ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, titanium dioxide and barium sulfate. 

21. The process according to claim 13, wherein the pH of the aqueous composition comprising at least one fiber stock is adjusted to a value in the range from 4 to 11. 

22. The process according to claim 13, wherein the step of adding methanesulfonic acid to the aqueous composition comprising at least one fiber stock takes place in a paper machine approach flow. 

23. The process according to claim 13, wherein the papery article is selected from graphic paper, office communication paper, packaging paper, board, card, hygiene paper and spe› cialty paper. 

24. The process according to claim 13, wherein the papery article is a packaging material for the food sector. 

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