an abhidharma collection, and that it likely contained five or six books. Caitika The Caitikas included a number of sub-sects including the Pūrvaśailas, Aparaśailas, Siddhārthikas, and Rājagirikas. In the 6th century CE, Avalokitavrata writes that Mahāyāna sūtras such as the Prajñāparamitā and others are chanted by the Aparaśailas and the Pūrvaśailas. Also in the 6th century CE, Bhāvaviveka speaks of the Siddhārthikas using a Vidyādhāra Piṭaka, and the Pūrvaśailas and Aparaśailas both using a Bodhisattva Piṭaka, implying collections of Mahāyāna texts within these Caitika schools. Bahuśrutīya The Bahuśrutīya school is said to have included a Bodhisattva Piṭaka in their canon. The , also called the , is an extant abhidharma from the Bahuśrutīya school. This abhidharma was translated into Chinese in sixteen fascicles (Taishō Tripiṭaka 1646). Its authorship is attributed to Harivarman, a third-century monk from central India. Paramārtha cites this Bahuśrutīya abhidharma as containing a combination of Hīnayāna and Mahāyāna doctrines, and Joseph Walser agrees that this assessment is correct. Prajñaptivāda The Prajñaptivādins held that the Buddha's teachings in the various piṭakas were nominal (Skt. prajñapti), conventional (Skt. ), and causal (Skt. hetuphala). Therefore, all teachings were viewed by the Prajñaptivādins as being of provisional importance, since they cannot contain the ultimate truth. It has been observed that this view of the Buddha's teachings is very close to the fully developed position of the Mahāyāna sūtras. Sārvāstivāda Scholars at present have "a nearly complete collection of sūtras from the Sarvāstivāda school" thanks to a recent discovery in Afghanistan of roughly two-thirds of Dīrgha Āgama in Sanskrit. The Madhyama Āgama (Taishō Tripiṭaka 26) was translated by Gautama Saṃghadeva, and is available in Chinese. The Saṃyukta Āgama (Taishō Tripiṭaka 99) was translated by Guṇabhadra, also available in Chinese translation. The Sarvāstivāda is therefore the only early school besides the Theravada for which we have a roughly complete Sūtra Piṭaka. The Sārvāstivāda Vinaya Piṭaka is also extant in Chinese translation, as are the seven books of the Sarvāstivāda Abhidharma Piṭaka. There is also the encyclopedic Abhidharma Mahāvibhāṣa Śāstra (Taishō Tripiṭaka 1545), which was held as canonical by the Vaibhāṣika Sarvāstivādins of northwest India. Mūlasārvāstivāda Portions of the Mūlasārvāstivāda Tripiṭaka survive in Tibetan translation and Nepalese manuscripts. The relationship of the Mūlasārvāstivāda school to Sarvāstivāda school is indeterminate; their vinayas certainly differed but it is not clear that their Sūtra Piṭaka did. The Gilgit manuscripts may contain Āgamas from the Mūlasārvāstivāda school in