Vietnamese poetry originated in the form of folk poetry and proverbs. Vietnamese poetic structures include six-eight, double-seven six-eight, and various styles shared with Classical Chinese poetry forms, such as are found in Tang poetry; examples include verse forms with ""seven syllables each line for eight lines,"" ""seven syllables each line for four lines"" (a type of quatrain), and ""five syllables each line for eight lines."" More recently there have been new poetry and free poetry.With the exception of free poetry, a form with no distinct structure, other forms all have a certain structure. The tightest and most rigid structure was that of the Tang Dynasty poetry, in which structures of content, number of syllables per line, lines per poem, rhythm rule determined the form of the poem. This stringent structure restricted Tang poetry to the middle and upper classes and academia.