The condensation products obtained by the reaction of urea or melamine with formaldehyde. Resinous condensation products of formaldehyde with other nitrogen-containing compounds, for example, aniline and amides, also belong to this group of resins but have gained only limited utility. Resins derived from the condensation of formaldehyde with urea, melamine, aniline, and p-toluene sulfonamide are discussed below.