The three periods of the Buddha's teaching as defined by Paramārtha: (a) 轉法輪 the first rolling onwards of the Law-wheel, the first seven years' teaching of Hīnayāna, i.e. the 四諦 four axioms and 空 unreality; (b) 照法輪 illuminating or explaining the law-wheel, the thirty years' teaching of the 般若prajñāor wisdom sūtras, illuminating 空 and by 空 illuminating 有 reality; (c) 持法輪 maintaining the law-wheel, i.e. the remaining years of teaching of the deeper truths of 空有 both unreality and reality. Also the three-fold group of the Lotus School: (a) 根本法輪 radical, or fundamental, as found in the 華嚴經 sūtra; (b) 枝末法輪 branch and leaf, i.e. all other teaching; until (c) 攝末歸本法輪 branches and leaves are reunited with the root in theLotus Sutra, 法華經.