и википедии достаточно https://ru.wikipedia.org/wiki/%CB%E8%F2%E2%E0#.D0.A0.D0.B5.D1.87.D1.8C_.D0.9F.D0.BE.D1.81.D0.BF.D0.BE.D0.BB.D0.B8.D1.82.D0.B0.D1.8F