. "Other useful additives having an active hydrogen compound include amides such as urea proper or other ureas, e.g., cyclic ethyleneurea, allylurea and thiourea, acetamide, malonamide and acrylamide as well as sulfonamides such as methanesulfonamide; carbamates such as ethylcarbamate or hydroxyethylcarbamate; and so on." . . .