Ключевые слова: abstract, ad, advertisement, advertising, aged, backdrop, background, backgrounds, billboard, black, blackboard, blackboards, blank, board, business, chalk, chalkboard, class, classroom, close, closeup, communication, dark, dirty, drawing, dust, education, empty, frame, grainy, gray, grunge, grungy, learn, lesson, old, rough, school, smudge, smudged, student, surface, teacher, text, texture, used, wall, white, wood, wooden,