Ключевые слова: abstract, background, big, blank, blank envelopes, blurred, business, clean, communication, copy space, correspondence, cover, delivery, document, empty, envelope, express, group, heap, isolated, large, large group of objects, letter, mail, many, message, nobody, note, object, office, package, packet, packing, paper, post, postal, postal service, selective focus, send, service, stack, stamp, stationery, supply, white, white background,