The Vietnamese Post has issued a series of stamps dedicated to Quan ho Bac Ninh. This is the name of folk songs of Northern delta of Vietnam. The songs are performed as alternating verses between two women from one village who sing in harmony, and two men from another village who respond with similar melodies. It is also a form of instant exchange of love between men and women. Quan ho Bac Ninh is recognized as the cultural heritage intangible representation of humanity by UNESCO.