Most national advertising includes embedding [of hidden stimuli]. Retail or local ad layouts may not have the facilities, as their artists and writers either do not know about subliminal techniques or they lack the skill and craftsmanship required to do the work well. Every major advertising agency has at least one embedding technician in its art department. The technique is taught in most commercial art schools.

Subliminal Seduction: Ad Media's Manipulation of a Not So Innocent America, 1974, p. 108.