. "s, such as for example N,N'-dimethyl-N,N'-diacetylsulfurylamide and N,N'-diethyl-N,N'-dipropionylsulfurylamide, triacylcyanurates, for example triacetyl or tribenzoyl cyanurate, carboxylic acid anhydrides, for example benzoic acid anhydride, m-chlorobenzoic acid anhydride, phthalic acid anhydride, 4-chlorophthalic acid anhydride, sugar esters, such as for example glucose pentaacetate, 1,3-diacyl-4" . . .