Besides the works of Asaṅga and Vasubandhu outlined above, the Yogācāra tradition as it is understood in Tibetan Buddhism is also based on a series of texts called the "Five Dharmas of Maitreya". These are the "Mahāyānasūtrālamkāra, Dharmadharmatāvibhāga, Madhyāntavibhāgakārikā, Abhisamayalankara" and the "Ratnagotravibhaga." These texts are traditionally said to have been related to Asaṅga by the Bodhisattva Maitreya from Tusita Heaven. According to D.S. Ruegg, the "five works of Maitreya" are mentioned in Sanskrit sources from only the 11th century onwards. As noted by S.K. Hookham and Paul Williams, their attribution to a single author has been questioned by modern scholars, especially the "Abhisamayalankara" and the "Ratnagotravibhaga" (which focuses on "tathāgatagarbha"). There are also various commentaries on these texts from Indian and Tibetan authors that are important in the Tibetan scholastic tradition.