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Craft of Poetry: Couplet
Well detailed discussion of the use of the couplet in poetry. A number of different kinds of couplets are defined and explained (short couplet, split couplet, heroic couplet, Alexandrine couplet, Qasida), and a "How To" section suggests...
Encyclopedia Britannica
Encyclopedia Britannica: Guide to Shakespeare:couplet
This is a small section of a much larger article on Shakespeare and the Globe Theater that discusses the use of couplets in poetry. Some different types of couplets are discussed (formal or closed, run-on or enjambment, alexandrine,...