Ключевые слова: address, airmail, anniversary, bill, black pen, card, celebration, communication, concept, congratulation, copy space, correspondence, craft, delivery, document, education, email, envelope, exchange, holding, hong kong, hong kong flag, hongkonger, honkongese, investment, invitation, letter, letter of happiness, mail, mailing, message, modern, national, national holiday, nationality, paper, payment, pen, pictogram, post, post office, postage, postcard, registration, retro postage, student, symbol,