Bagpipes were alluded to in Europe as early as the 9th century; earlier evidence is scarce but includes four Latin and Greek references of about ad 100 and, possibly, an Alexandrian terra-cotta of about 100bc (at Berlin). In the earliest ones the bag is typically a bladder or a whole sheepskin or goatskin, minus the hindquarters; later, two pieces of skin were cut to shape and sewn together. Bagpipes have always been folk instruments, but after the 15th century some were used for court music, and others have survived as military instruments.