Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Lemon Incest
The title is a play on words in French in the chorus between "Un zeste de citron" ("A lemon zest") and "Inceste de citron" ("lemon incest").