Abstract: According to the invention, a process of making paper comprises forming a cellulosic suspension, adding retention aid to the suspension, draining the suspension through a screen to form a sheet, and drying the sheet and in this process we add to the suspension a retention system comprising polyethylene oxide and a greater amount (dry weight) of a phenolsulphone-formaldehyde resin (PSR resin) consisting essentially of recurring units of the formula--CH.sub.2 --X--wherein (a) 10 to 100% of the groups X are di(hydroxyphenyl) sulphone groups, (b) 0 to 90% of the groups X are selected from hydroxy phenyl sulphonic acid groups (i.e., groups which contain at least one hydroxy-substituted phenyl ring and at least one sulphonic group) and naphthalene sulphonic acid groups and (c) 0 to 10% of the groups X are other aromatic groups.