a separate collection of texts called the Nyingma Gyubum, assembled by Ratna Lingpa in the 15th century and revised by Jigme Lingpa. Among Tibetans, the main language of study is classical Tibetan, however, the Tibetan Buddhist canon was also translated into other languages, such as Mongolian and Manchu. During the Yuan, Ming, and Qing dynasties, many texts from the Tibetan canon were also translated into Chinese. Numerous texts have also recently been translated into Western languages by Western academics and Buddhist practitioners. Sutras Among the most widely studied sutras in Tibetan Buddhism are Mahāyāna sutras such as the Perfection of Wisdom or Prajñāpāramitā sutras, and others such as the Saṃdhinirmocana-sūtra, and the Samādhirāja Sūtra. According to Tsongkhapa, the two authoritative systems of Mahayana Philosophy (viz. that of Asaṅga - Yogacara and that of Nāgārjuna - Madhyamaka) are based on specific Mahāyāna sūtras: the Saṃdhinirmocana Sūtra and the Questions of Akṣayamati (Akṣayamatinirdeśa Sūtra) respectively. Furthermore, according to Thupten Jinpa, for Tsongkhapa, "at the heart of these two hermeneutical systems lies their interpretations of the Perfection of Wisdom sūtras, the archetypal example being the Perfection of Wisdom in Eight Thousand Lines." Treatises of the Indian masters The study of Indian Buddhist treatises called shastras is central to Tibetan Buddhist scholasticism. Some of the most important works are those by the six great Indian Mahayana authors which are known as the Six Ornaments and Two Supreme Ones (Tib. gyen druk chok nyi, Wyl. rgyan drug mchog gnyis), the six being: Nagarjuna, Aryadeva, Asanga, Vasubandhu, Dignaga, and Dharmakirti and the two being: Gunaprabha and Shakyaprabha (or Nagarjuna and Asanga depending on the tradition). Since the late 11th century, traditional Tibetan monastic colleges generally organized the exoteric study of Buddhism into "five great textual traditions" (zhungchen-nga). Abhidharma Asanga's Abhidharma-samuccaya Vasubandhu's Abhidharma-kośa Prajnaparamita Abhisamayalankara Shantideva's Bodhisattvacaryāvatāra Madhyamaka Nagarjuna's Mūlamadhyamakakārikā Aryadeva's Four Hundred Verses (Catuhsataka) Candrakīrti's Madhyamakāvatāra Śāntarakṣita's Madhyamākalaṃkāra Shantideva's Bodhisattvacaryāvatāra Pramana Dharmakirti's Pramāṇavarttika Dignāga's Pramāṇa-samuccaya Vinaya Gunaprabha's Vinayamula Sutra Other important texts Also of great importance are the "Five Treatises of Maitreya" including the influential Ratnagotravibhāga, a compendium of the tathāgatagarbha literature, and the Mahayanasutralankara, a text on the Mahayana path from the Yogacara perspective, which are often attributed to Asanga. Practiced focused texts such as the Yogācārabhūmi-Śāstra and Kamalaśīla's Bhāvanākrama are the major sources for meditation. While the Indian texts are often central, original material by key Tibetan scholars is also widely studied and collected